| O & F CATERING LTD | Hampshire | A rating |
| O & H Catering Ltd | Lyndhurst | A rating |
| O & S STORES LTD | Nelson | A rating |
| O A EDWARDS LIMITED T/A LANDSDOWNE PHARMACY | PETERBOROUGH | A rating |
| O B S Oldham Ltd | Manchester | A rating |
| O Brown's Restaurant Ltd | Bristol | A rating |
| O C Accountants Ltd | Newcastle upon Tyne | A rating |
| O Cudmore Ltd | Petworth | A rating |
| O I E Investments Ltd trading as Central Hoxton Hotel | London | A rating |
| O K (UK) LTD T/A BRUNCH CAFE AND GRILL | LONDON | A rating |
| O S & Ali Services(London) Limited | Manchester | A rating |
| O Shaped Lawyer Limited | London | A rating |
| O Stone UK Ltd | greys | A rating |
| O W Stuart Ltd | London | A rating |
| O-I Glass Limited | HARLOW | A rating |
| O-Innovations | Morecambe | A rating |
| O-Matcha Ltd | London, | A rating |
| O-NET PHOTONICS (UK) LIMITED | Southampton | A rating |
| O. Heap & Son (Derby) Limited | Derby | A rating |
| O. P. L. Limited | London | A rating |
| O.C.L. Facades Limited | Basildon | A rating |
| O.S. Energy (UK) Ltd | Newcastle Upon Tyne | A rating |
| O.S.T.C. LIMITED | Bromley | A rating |
| O' Kane Meats (NI) Ltd | Derry | A rating |
| O'Connor Burke Architecture Ltd | Londonderry | A rating |
| O'Connor Sutton Cronin & Associates (Belfast) Ltd | Belfast | A rating |
| O'Connor Sutton Cronin & Associates (London) Ltd | London | A rating |
| O'Connors Legal Services Limited | Liverpool | A rating |
| O'Halloran and O'Brien | Surrey | A rating |
| O'HARA WASTE OIL LIMITED | Denham | A rating |
| O'Hares Supermarket Ltd | Newry | A rating |
| O'Kane Woodworking 2010 Limited | Dungiven | A rating |
| O'Law Associate Limited | Sutton | A rating |
| O'Malley Haulage Limited | Watford | A rating |
| O'Melveny & Myers LLP | London | A rating |
| O'Neill Engineering Consultancy Limited | High Wycombe | A rating |
| O'Neill Fencing Limited | Strabane | A rating |
| O'Neill Modernmedia (OMM) Ltd | Maidenhead | A rating |
| O'Reilly Precast Limited | Barry | A rating |
| O'RICH LTD | Chelmsford | A rating |
| O'sarracino Pizzeria LTD | Sandy | A rating |
| O'Shea Healthcare Ltd | Liverpool | A rating |
| O'Toid Opticians | Frome | A rating |
| O'Toole International Logistics Ltd | Bellshill | A rating |
| O&C LTD | London | A rating |
| O&E 1618 LTD | Camberley | A rating |
| O&F Catering Ltd | Ferndown | A rating |
| O&H VEHICLE CONVERSIONS GROUP LIMITED | Goole | A rating |
| O&S Nurseries Ltd | London | A rating |
| O2 CARE LTD | Bexley | A rating |
| O2 CATERING LIMITED | LONDON | A rating |
| o2h Ltd | Cambridge, London | A rating |
| O3 Facilities Management LTD | Leicester | A rating |
| o9 Solutions UK Limited | London | A rating |
| OA TRADING LIMITED | Manchester | A rating |
| OADBY SUSHI LIMITED | Leicester | A rating |
| OADIGITALS LTD | Wakefield | A rating |
| OAG Aviation Worldwide Ltd | Luton | A rating |
| OAK and PAX Limited | Redhill | A rating |
| OAK BAR AND GRILL LIMITED | Birmingham | A rating |
| Oak Care Home Ltd | Enfield | A rating |
| Oak Care Home Services Ltd | York | A rating |
| Oak Care Limited | Hemel Hempstead | A rating |
| OAK COTTAGE CARE LTD | HATFIELD | A rating |
| Oak Court Care Home | Norwich | A rating |
| OAK ENGAGE LIMITED | Newcastle Upon Tyne | A rating |
| Oak Farm (Taverham) Limited | Norwich | A rating |
| Oak Farm Court Limited | Norwich | A rating |
| Oak Forest Joinery Contractors Ltd T/A Oak forest of Yorkshire | Bradford | A rating |
| Oak Group Ltd | Brierley Hill | A rating |
| Oak Healthcare Holding Ltd | Brierley Hill | A rating |
| Oak Hill Advisors (U.K. Services) Limited | London | A rating |
| Oak Hill Theological College | London | A rating |
| Oak House | Exeter | A rating |
| Oak House Care Ltd t/a Oak House Care Home | Cardiff | A rating |
| Oak House Children's Homes Ltd | Ilford | A rating |
| Oak House Dental Practice | Truro | A rating |
| OAK HOUSE HOMECARE CAMBS LTD | Peterborough, United Kingdom | A rating |
| OAK HOUSE HOMECARE LTD | Yaxley | A rating |
| OAK INITIATIVE UK CIC | City of Bradford | A rating |
| Oak Joinery Limited | London | A rating |
| Oak Lea Hotel | Blackpool | A rating |
| OAK LEAF STORES | Stockton-on-Tees | A rating |
| Oak Mount Developments Limited | Kent | A rating |
| Oak Nest Children's Homes Ltd | Erith | A rating |
| Oak Philanthropy (UK) Limited | London | A rating |
| Oak Security Services Limited | Ilford | A rating |
| OAK Servco Limited | London | A rating |
| Oak Smart Technology Limited | Leicester | A rating |
| Oak Solicitors Limited t/a Oak Legal | London | A rating |
| Oak Support Limited | Twickenham | A rating |
| Oak Tree Loch Lomond LTD | Glasgow | A rating |
| Oak Tree Lodge | Southampton | A rating |
| Oak Tree Mews | Gloucestershire | A rating |
| OAK TREE PRE-SCHOOL NURSERIES LIMITED | LONDON | A rating |
| Oak Tree Surgery | BRIDGEND | A rating |
| OAK TREE TAXATION LTD | LONDON | A rating |
| Oak Vale Medical Centre | Liverpool | A rating |
| Oak View Primary and Nursery School | Hatfield | A rating |
| Oak Wood School | Uxbridge | A rating |
| OAK&KAPOK LIMITED | Colchester | A rating |
| Oak33 Ltd | Manchester | A rating |
| Oaka Group | Peterborough | A rating |
| OAKA Vending (UK) Limited | Glasgow | A rating |
| Oakamoor Cricket Club | Stoke-on-Trent | A rating |
| Oakbank Waste Management Ltd | Dumfries | A rating |
| Oakbrook Finance Ltd | Notts | A rating |
| OAKCEAN CAPITAL LIMITED | Mayfair, London | A rating |
| Oakdale Care Home Ltd | Essex | A rating |
| Oakdale Care Limited | Leicester | A rating |
| Oakdale House Trust | Luton | A rating |
| Oakdale Stores Ltd | Oakdale | A rating |
| Oakdale Veterinary Centre Ltd | Peterborough | A rating |
| Oakdene Autos | Basildon | A rating |
| Oakdene Care Home Ltd | Oldham | A rating |
| Oakdene Hollins Limited | Aylesbury | A rating |
| Oakdene Residential Home | Waterlooville | A rating |
| OAKDOWN HOUSE LIMITED | Burwash Common Etchingham | A rating |
| Oakengates Premier Stores | Oakengates | A rating |
| Oakes ElectricalSolutionsLtd | Studley | A rating |
| Oakfield Care (Ashtead) Ltd | Ashtead | A rating |
| Oakfield Health Centre | Gravesend | A rating |
| Oakfield House Care Limited | Canterbury | A rating |
| Oakfield Manor Estates Limited | Knutsford | A rating |
| Oakfield Nursery School Ltd | Altrincham | A rating |
| Oakfield Nursing Home | PRESTON | A rating |
| Oakfield Parkonians Cricket Club | Ilford | A rating |
| Oakfield Pharma Ltd | St Helens | A rating |
| Oakfield Psychological Services Limited | Altrincham | A rating |
| Oakfield Quality Homecare Limited t/a Right at Home Colchester and District | Colchester | A rating |
| Oakfoil Limited | Barnoldswick | A rating |
| Oakgrove Cabins Ltd | Derry | A rating |
| OAKHAM FISH LTD | OAKHAM | A rating |
| Oakham Grange - Ardale (Oakham) Ltd | Oakham | A rating |
| OAKHAM SCHOOL | OAKHAM | A rating |
| OakhamSupermarket Ltd | Oakham | A rating |
| Oakhaven Residential Care Home Limited | Cheltenham | A rating |
| Oakhill Hotel Limited | Matlock | A rating |
| Oakhill IT Solutions LLP | Hertfordshire | A rating |
| OAKLAND CAPITAL DEVELOPMENT LTD | THE BUTTS | A rating |
| Oakland Central Limited | Chigwell | A rating |
| OAKLAND COURT LIMITED | West Sussex | A rating |
| OAKLAND GROUP SERVICES LIMITED | Leeds | A rating |
| Oaklands care hove limited | Hove | A rating |
| Oaklands Care Services Limited | Kingston Upon Thames | A rating |
| Oaklands College | St Albans | A rating |
| Oaklands Farm Eggs Limited | Telford | A rating |
| Oaklands Health Centre | Huddersfield | A rating |
| Oaklands Manor Care Home Ltd T/A Oaklands Manor Nursing Home | Saltburn-by-the-sea | A rating |
| Oaklands Rest Home | Southampton | A rating |
| Oaklands SEN School Berkshire Limited | Hungerford | A rating |
| Oaklands Stores | St Albans | A rating |
| Oaklea Care | Somerset | A rating |
| Oakleaf Partnership Limited | London | A rating |
| Oakleigh Care Homes Limited | Huntingdon | A rating |
| oakleigh care homes ltd | Huntingdon | A rating |
| Oakleigh Fresh Limited | Waltham Abbey | A rating |
| OAKLEIGH GROUP OF PHARMACIES LIMITED | LONDON | A rating |
| Oakleigh Residential Home Limited | Swadlincote | A rating |
| Oakleigh SAS Consultancy Limited | Bradford | A rating |
| Oakley Accountancy Limited | Droitwich Spa | A rating |
| Oakley Capital Limited | London | A rating |
| Oakley carehomes limited | Romford | A rating |
| Oakley Farming Ltd | Shrewsbury | A rating |
| Oakley Grange Care Home | Warwick | A rating |
| Oakley Hall Park Limited | Basingstoke | A rating |
| Oakley Health Group | Blackwater | A rating |
| Oakley House Children Homes Ltd | London | A rating |
| Oakley house kent | Maidstone | A rating |
| Oakley Road Dental Practice Ltd | Southampton | A rating |
| Oakley Wine Agencies | Colchester | A rating |
| Oakley8 Limited | East Horsley | A rating |
| Oaklodge Care Home | Northampton | A rating |
| Oaklodge Nursing Home | Prestwich | A rating |
| OAKLODGE NURSING HOME | BURGESS HILL | A rating |
| Oaklodge Supporting Living Limited | London | A rating |
| Oaklon Limited | London | A rating |
| OAKLY LTD | Swansea | A rating |
| OAKLYN GARDENS LIMITED | Isle of Wight | A rating |
| Oakman Inns and Restaurants Limited | Berkhamsted | A rating |
| Oakman Lord LTD | Kington | A rating |
| Oakmere Contract Services Ltd | Upminster | A rating |
| OAKMERE SERVICE CENTRE | Potters Bar | A rating |
| Oakminster Healthcare Ltd | Glasgow | A rating |
| Oakmount Capital LLP | London | A rating |
| Oaknorth (UK) Limited | London | A rating |
| OakNorth Bank Plc | London | A rating |
| OAKRAY CARE GROUP LIMITED | Southampton | A rating |
| OAKS ASSET MANAGEMENT | Sevenoaks | A rating |
| Oaks Care Holdings Ltd | Sittingbourne | A rating |
| Oaks Healthcare | Waterlooville | A rating |
| Oaks Healthcare Ltd. | Spalding | A rating |
| Oaks Montessori Ltd | Newton Abbot | A rating |
| Oaks Park Ltd | Banstead | A rating |
| Oaks Properties Limited | New Castle Upon Tyne | A rating |
| Oaksfield Care Ltd | Grantham | A rating |
| Oakshed Care Ltd | Camborne | A rating |
| Oakside Pharm Ltd | Saltburn by the Sea | A rating |
| Oakside Surgery | Plymouth | A rating |
| Oaksmere Dental Surgery Partnership | Barnsley | A rating |