| NW Drain Solutions Ltd | London | 2025 |
| NW Drainage Solutions Ltd | Gaerwen | 2018 |
| NWE Waste Services Limited | Salford | 2018 |
| NWH Group Limited | Dalkeith | 2007 |
| NWH Waste Services (Middleton) Limited | Dalkeith | 2014 |
| NWP Holdco Limited | Belfast | 2018 |
| NWR Waste Brokers Limited | Blackburn | 2022 |
| NXS Limited | Gloucester | 1999 |
| NY Remedials Limited | Knaresborough | 2025 |
| O Apparel NG Limited | Newport | 2025 |
| O Donovan and Tonetto Limited | London | 2026 |
| O M Deehan & SON Ltd | Bishop'S Stortford | 2019 |
| O&D Waste Removal Limited | Cleethorpes | 2024 |
| O&K11 Limited | London | 2020 |
| O'Brien Metals Ltd | Cheltenham | 2017 |
| O'Brien Recycling Ltd | Lybster | 2010 |
| O'Brien's Waste Clearance Ltd | Bawtry | 2018 |
| O'Donnell Waste Management Ltd | Barnsley | 2011 |
| O'Donovan Brothers Ltd | Enfield | 2020 |
| O'Donovan Skip Hire Limited | Enfield | 2025 |
| O'Hara Bros. Construction Limited | Wembley | 2010 |
| O'Hara Waste Management Ltd | Bucks. | 2008 |
| O'Hara Waste OIL Limited | Northampton | 2012 |
| O'Neill & Brennan Site Services Limited | Lydney | 2002 |
| O'Neill Drain Services Ltd | Armagh | 2025 |
| O. & T.S. Catering Limited | Leeds | 1989 |
| O. Hatt Holdings Ltd | Reading | 2020 |
| O.L.D. Waste & Consultancy Ltd | Kingswinford | 2017 |
| O.R.M. North Norfolk Limited | Norwich | 2003 |
| O.T Waste Removal Ltd | Colchester | 2026 |
| O2E Recycling Technologies Ltd | London | 2016 |
| OAC Environmental Limited | Rotherham | 2016 |
| Oak Bank Solutions Ltd | Spalding | 2019 |
| Oak Material Solutions Ltd | Birmingham | 2025 |
| Oakfield Recycling Limited | Moorgreen | 2008 |
| Oakham Aggregates Limited | Ravenshead | 2025 |
| Oakham Road Sweepers Limited | Birmingham | 2016 |
| Oakland Traders Limited | London | 2025 |
| Oakland Water Services Ltd | Farnborough | 2024 |
| Oakleaf Recycling Limited | Staines-Upon-Thames | 2015 |
| Oakley Eco Ltd | Ickenham | 2024 |
| Oakstone FM Ltd | London | 2025 |
| Oakwood Furniture Frames Limited | London | 1990 |
| Oasis Waste Services Ltd | Cranleigh | 2025 |
| Oasis Water Treatment Ltd | Ramsgate | 2015 |
| Oates Environmental Limited | Rugby | 2000 |
| OB Metals Ltd | Liverpool | 2025 |
| OB Skips and Recycling Ltd | Liverpool | 2019 |
| OB Waste Management Ltd | London | 2022 |
| OB Waste Removals Ltd | Nuneaton | 2022 |
| OB Waste Solutions Ltd | Sheffield | 2025 |
| Oban Skip Hire Ltd. | Oban | 2004 |
| OBE Environmental Limited | Dartford | 2022 |
| OBI Engineering Ltd | Okehampton | 2015 |
| Obix Trade Ltd | Westcliff-On-Sea | 2020 |
| Observe Solutions Limited | Ongar | 2004 |
| Obsidian Environmental Limited | Birkenhead | 1999 |
| Occasional Furniture (Manufacturing) Limited | Dundee | 1987 |
| Occlude Drainage Solutions Limited | Witham | 2020 |
| OCE Systems Limited | Halesworth | 2004 |
| Oceala Limited | Telford | 1982 |
| Ocean Building Services Limited | St. Ives | 2013 |
| Ocean Loop Ltd | London | 2020 |
| Ocean Polymers Limited | Ascot | 2017 |
| Ocean Recycling Limited | Dagenham | 2025 |
| Ocean Resource Management Ltd | Birmingham | 2018 |
| Ocean Saviour Limited | Southampton | 2018 |
| Ocmis Limited | Episcopi, Martock | 1984 |
| Octagon Green Solutions Limited | Leeds | 2012 |
| Octane Draincare Limited | Padiham | 2018 |
| Octane Holding Group Limited | Padiham | 2012 |
| Octavian Lifting Ltd | Harrow | 2026 |
| October House Environmental Limited | Scunthorpe | 2003 |
| Ocwaas Limited | Abingdon | 2025 |
| Odessalux Ltd | Peterborough | 2023 |
| Odin Power and Energy Limited | Redcar | 2025 |
| Odour Control Ltd | Southampton | 2007 |
| ODP Waste Management Ltd | Rayleigh | 2026 |
| OEP Services Ltd | Birmingham | 2023 |
| Off-Tech (UK) Limited | Bolton | 2003 |
| Office Reuse Ltd | London | 2026 |
| Offload & GET RID - Oldham Ltd | Saddleworth | 2025 |
| Ofield's Skip Hire Ltd | Bolton | 2020 |
| OG Waste Removal Services Ltd | Bradford | 2025 |
| Ogden Skip Hire Limited | Manchester | 2003 |
| OGH Contractors Ltd | Rye | 2014 |
| Ohali Logistics Ltd | Ashford | 2026 |
| Ohsogreengardens Ltd | Chichester | 2025 |
| OIL - Green Life 2023 Ltd | Enfield | 2023 |
| OIL Facilities Limited | Cowbridge | 2007 |
| OIL Holdings Ltd | Chester | 2019 |
| OIL Recoveries Limited | Ormskirk | 2010 |
| OIL Recycling Company Limited | Bidford On Avon | 2018 |
| OIL X OIL Ltd | London | 2025 |
| OJC Commodities Limited | Belfast | 2024 |
| OJH Services Ltd | Bromley | 2026 |
| OK Skips Ltd | Bridgnorth | 2019 |
| Okemah Limited | Wishaw | 1982 |
| Okoparc Limited | London | 2025 |
| Olafek Trading Ltd | Upminster | 2015 |