Construction Company Index - O
- O A Steel Fabrication - London
- O B Y Ltd. - Warrington
- O'Boyle Civil Engineering Ltd. - Lincoln
- O'Brien Contractors Ltd - Leamington Spa
- O'Connor Construction Co. Ltd. - Cheltenham
- O'Connor Utilities Ltd. - Manchester
- O'Donnell Developments Ltd. - Birmingham
- O'Donnell Michael A - Wakefield
- O'Hagan Plant - Newry
- O'Keefe Construction (Greenwich) Ltd. - London
- Oak Tree GB Ltd - Royston
- Oakbray Ltd - Stoke on Trent
- Oakdale Design Services Ltd. - Newport
- Oakfield Construction C Eng Ltd. - Nottingham
- Oakleaf Conservatories Ltd. - York
- Oakley Mini Diggers - Basingstoke
- Oakley Plant Ltd - Scarborough
- Oakmace Exhibitions Ltd. - Waltham Abbey
- Oakmasters - Haywards Heath
- Oaksmere Refrigeration Design & Consultancy Ltd. - Stowmarket
- Oakwood Construction (Derby) Ltd. - Derby
- Oakwood Plant Group Ltd. - London
- Ocean Corporate Hygiene - Sunbury on Thames
- Oeg Offshore Ltd. - Aberdeen
- Oftenwell Ltd. - Mold
- Ogilvie Group Ltd - Stirling
- Ogley Brothers Ltd. - Sheffield
- Ohgon Electronics - Canvey Island
- Okeland Ltd - Cranleigh
- Old Station Quarry - Somerton
- Oldfield C & R - Bristol
- Oleo International Ltd - Coventry
- Oliveti Cubicles Ltd - Leicester
- Olivewood Ltd. - Edgware
- Olympic Conveyor Services Division - Bodmin
- OM Support - Northwich
- Omega Research Ltd - Ely
- Omega Technical Services Ltd. - Romney Marsh
- Omega Tile Ltd - Redditch
- Omni Sensors and Transmitters Ltd - Leamington Spa
- Omos Ltd - Naas
- One Offs Ltd. - Liverpool
- Onestop Testing Services - Bognor Regis
- Onsite Services - Southampton
- Onyx europe Ltd - Penryn
- Opti-cal Survey Equipment Ltd - Reading
- Optima Design Associates Ltd - Mansfield
- Optime Lighting Ltd. - Hitchin
- Orbital Equipment Ltd. - Waltham Abbey
- Orchard Hire and Sales Ltd - Cheltenham
- Orchard Plant - Wellingborough
- Orford Plant Hire - Bromsgrove
- Original Features (Restorations) Ltd. - London
- Orion Engineering Ltd. - Nantwich
- Orkney Aggregates Ltd. - Orkney
- Orlight Ltd - Potters Bar
- Orpington Timber & Building Supplies Ltd. - Bexleyheath
- Orthos Projects Ltd. - Market Harborough
- Osborne and Collins - Walton on Thames
- Osborne Fabrications - Wigton
- Osco Ltd - Bletchley
- Oscura Ltd. - Reading
- Osgood Brothers Ltd. - Horsham
- Oso Hotwater (U K ) Ltd. - Gateshead
- Ossett Mouldings Ltd. - Dewsbury
- Oswald Record Plant Sales (Midlands) Ltd. - Chesterfield
- Oswestry Industrial Buildings Ltd - Oswestry
- Otford Builders Merchants Ltd. - Sevenoaks
- Otis Ltd - London
- OV Ford Plant Hire Services - Bridgend
- Ove Arup & Partners - Bristol
- Ovenden Associates - Southport
- Overcourt Ltd. - London
- Owen J & Sons - Dolgellau
- Owen D Collins Plant Hire - Salisbury
- Owen Joinery (Fires) - Llanelli
- Owen Mullen (Contractors) Ltd. - Sittingbourne
- Owen Pell Ltd. - Hereford
- Owen Pugh & Co. Ltd. - Cramlington
- Owen R D & G - Shrewsbury
- Owens-Corning Veil U K Ltd. - Liversedge
- Oxley Garage Doors Ltd. - Hull
- Oxus Services Ltd. - Woking
- Oxyburn Ltd. - Halesowen