UK BBC and commercial radio stations containing Radio O in the name:
Absolute Radio Country [ACN]
Adventist Radio London [ADV]
Angel Radio (Chichester, Portsmouth & Havant) [AGH]
Bailiwick Radio (formerly Bailiwick Radio Hits) [BWK]
BBC Radio 5 Sports Extra [B5S]
BBC Radio Bristol [BBR]
BBC Radio Cornwall [BCN]
BBC Radio Devon [BDV]
BBC Radio Foyle [BFY]
BBC Radio Gloucestershire [BGT]
BBC Radio Lincolnshire [BLC]
BBC Radio London [BLN]
BBC Radio Norfolk [BNF]
BBC Radio Northampton [BNH]
BBC Radio Nottingham [BNT]
BBC Radio Orkney [BOK]
BBC Radio Oxford [BOX]
BBC Radio Scotland (Network FM) [BSL]
BBC Radio Scotland (MW) [BSA]
BBC Radio Shropshire [BSH]
BBC Radio Solent (South Hampshire, Isle of Wight & East Dorset) [BSC]
BBC Radio Solent (West Dorset) [BSD]
BBC Radio Somerset [BSS]
BBC Radio Stoke [BST]
BBC Radio Suffolk [BSF]
BBC Radio Wales (Network FM) [BWL]
BBC Radio York [BYK]
Coast and County Radio (Hull & East Yorkshire) (formerly Great Yorkshire Radio) [CAH]
Coast and County Radio (North Yorkshire) [CAC]
Divine Radio London [DVN]
Dragon Radio (North) [DGN]
Dragon Radio (South) [DRG]
Energy Radio (London) [ENL]
Frisk Radio (North East) [FSK]
GenX Radio Suffolk [GNX]
Glow Radio (Basingstoke) [GLB]
Greatest Hits Radio (Berkshire & North Hampshire) [GBH]
Greatest Hits Radio (Black Country & Shropshire) [GBS]
Greatest Hits Radio (Bristol, Bath & the West) [GBB]
Greatest Hits Radio (Cornwall) [GCN]
Greatest Hits Radio (Coventry & Warwickshire) [GCW]
Greatest Hits Radio (Cumbria & South West Scotland) [GCM]
Greatest Hits Radio (Devon) [GDV]
Greatest Hits Radio (Dorset) (Bournemouth & Poole) [GBP]
Greatest Hits Radio (Dorset) (North & West Dorset) [GDS]
Greatest Hits Radio (East Yorkshire & Northern Lincolnshire) [GHM]
Greatest Hits Radio (Gloucestershire) [GGT]
Greatest Hits Radio (Harrogate & the Yorkshire Dales) [GHD]
Greatest Hits Radio (Herefordshire & Worcestershire) [GHW]
Greatest Hits Radio (Ipswich & Suffolk) [GSF]
Greatest Hits Radio (Lincolnshire) [GLC]
Greatest Hits Radio (Liverpool & the North West) [GMS]
Greatest Hits Radio (London) [GLN]
Greatest Hits Radio (Manchester & the North West) [GMC]
Greatest Hits Radio (Norfolk & North Suffolk) [GNF]
Greatest Hits Radio (North East) (Teesside) [GTS]
Greatest Hits Radio (North East) (Tyne & Wear) [GTW]
Greatest Hits Radio (North Wales) [GNW]
Greatest Hits Radio (Northamptonshire) [GNH]
Greatest Hits Radio (Northern Ireland) [GNI]
Greatest Hits Radio (Oxfordshire) [GOX]
Greatest Hits Radio (Peterborough, Stamford & Rutland) [GSR]
Greatest Hits Radio (Plymouth) [GPM]
Greatest Hits Radio (Scotland) (Ayrshire) [GAY]
Greatest Hits Radio (Scotland) (Dumfries & Galloway) [GDG]
Greatest Hits Radio (Scotland) (Edinburgh, the Lothians, Fife & Falkirk) [GED]
Greatest Hits Radio (Scotland) (Glasgow & the West) [GGL]
Greatest Hits Radio (Scotland) (North East Scotland) [GAB]
Greatest Hits Radio (Scotland) (The North of Scotland) [GNS]
Greatest Hits Radio (Scotland) (Scottish Borders & North Northumberland) [GBD]
Greatest Hits Radio (Scotland) (Tayside & Fife) [GTY]
Greatest Hits Radio (Somerset) [GSS]
Greatest Hits Radio (South Coast) [GHS]
Greatest Hits Radio (South Wales) [GSW]
Greatest Hits Radio (South Yorkshire & North Derbyshire) (High Peak & Hope Valley) [GHP]
Greatest Hits Radio (South Yorkshire & North Derbyshire) (North East Derbyshire) [GND]
Greatest Hits Radio (South Yorkshire & North Derbyshire) (South Yorkshire) [GSY]
Greatest Hits Radio (Staffordshire & Cheshire) [GST]
Greatest Hits Radio (Swindon) [GSN]
Greatest Hits Radio (West Norfolk) [GWN]
Greatest Hits Radio (West Yorkshire) [GWY]
Greatest Hits Radio (York & North Yorkshire) [GYK]
Greatest Hits Radio (Yorkshire Coast) [GYC]
Hits Radio (Berkshire & North Hampshire) [HBN]
Hits Radio (Black Country & Shropshire) [HBS]
Hits Radio (Cornwall) [HCO]
Hits Radio (County Durham, Northumberland and Tyne & Wear) [HNE]
Hits Radio (Coventry & Warwickshire) [HCW]
Hits Radio (Cumbria & South West Scotland) [HCM]
Hits Radio (Devon) [HDV]
Hits Radio (Dorset) [HBP]
Hits Radio (East Yorkshire) [HHM]
Hits Radio (Glasgow) [HGL]
Hits Radio (Gloucestershire) [HGS]
Hits Radio (Herefordshire & Worcestershire) [HHW]
Hits Radio (Lincolnshire & Newark) [HLI]
Hits Radio (Liverpool) [HMS]
Hits Radio (London) [HLD]
Hits Radio (Norfolk) [HNO]
Hits Radio (North East Scotland) [HAB]
Hits Radio (The North of Scotland) [HNS]
Hits Radio (North Wales) [HAG]
Hits Radio (North Yorkshire) [HNY]
Hits Radio (Northamptonshire) [HNN]
Hits Radio (Northern Ireland) [HNI]
Hits Radio (Oxfordshire) [HOF]
Hits Radio (Peterborough) [HPT]
Hits Radio (South Coast) [HSO]
Hits Radio (South Wales) [HWL]
Hits Radio (South Yorkshire) [HSY]
Hits Radio (Staffordshire & Cheshire) [HST]
Hits Radio (Suffolk) [HSK]
Hits Radio (Swindon) [HSN]
Hits Radio (West of England) [HWE]
Hits Radio (West Yorkshire) [HWY]
Isle of Wight Radio Retro [IWR]
Like Radio (formerly Like ONE) [LIK]
Lyca Radio (London) [LYC]
Magic Radio (London & Bristol) [MLN]
Mixtape Radio (formerly Like RETRO) [MXT]
More Radio (Eastbourne) [MRE]
More Radio (Worthing) [MRW]
More Radio Retro [MRR]
Nation Easy Radio (Dorset) [NED]
Nation Easy Radio (Portsmouth) [NEP]
Nation Easy Radio (Southampton & Winchester) [NEH]
Nation Radio (London) [NLN]
Nation Radio (North East) [NNE]
Nation Radio (Scotland) [NGL]
Nation Radio (South) (Dorset) [NDS]
Nation Radio (South) (South Hampshire & Isle of Wight) [NHS]
Nation Radio (South) (Sussex) [NSX]
Nation Radio (Suffolk) [NSF]
Nation Radio (Wales) (Ceredigion & North Wales) [NCD]
Nation Radio (Wales) (South East) [NWL]
Nation Radio (Wales) (South West) [NWW]
Nation Radio (Westcountry) (Cornwall) [NCN]
Nation Radio (Westcountry) (Devon) [NDV]
Nation Radio (Westcountry) (Somerset) [NSS]
Nation Radio (Yorkshire) [NHM]
North East Radio Scotland [NES]
Positive Radio (formerly The Power Station) [PST]
Premier Christian Radio (London) [PCL]
PRL, Polskie Radio Londyn - Polish Radio London [PRL]
Q Radio (Coleraine) [QCR]
Q Radio (Londonderry) [QDR]
Q Radio (Newry & Mourne) [QNR]
Q Radio (Omagh & Enniskillen) [QOE]
Radio Broadstairs [BDS]
Radio Caroline Flashback [CRF]
Radio Exe (Plymouth) [EXP]
Radio Matryoshka [MAT]
Radio North Angus [RNA]
Radio O [RDO]
Radio Pembrokeshire [PEM]
Radio Victory [VIC]
Radio West Norfolk [WNF]
Radio Woking (CEASED) [WOK]
Radio X (London) [XLN]
Radio X Classic Rock [XCR]
Rewind Radio (Cornwall) [RWD]
Rother Radio (Doncaster & Thorne) [RTD]
RWR, Radio Wester Ross [RWR]
Smooth Radio (East Midlands) (Northamptonshire & Peterborough) [SNP]
Smooth Radio (Gloucestershire) (CEASED) [SGT]
Smooth Radio (London) [SLN]
Smooth Radio (North East) (Teesside) [STS]
Smooth Radio (North East) (Tyne & Wear) [STW]
Smooth Radio (North West) [SNW]
Smooth Radio (Scotland) [SSL]
Smooth Radio (South Coast) [SSC]
Smooth Radio (South West) [SSW]
Smooth Radio (Wales) (North Wales) [SAG]
Smooth Radio (Wales) (South Wales) [SWS]
Smooth Radio (Westcountry) [SWC]
STV Radio (Ayrshire & North of Scotland) [STV]
STV Radio (Central Scotland) [STC]
STV Radio (North East Scotland) [STA]
Sunrise Radio (London) [SRL]
Sunrise Radio (Yorkshire) [SRY]
Sunrise Radio Gold [SRG]
Sunshine Radio (Herefordshire) [SSH]
Sunshine Radio (Monmouthshire) [SSM]
Sunshine Radio (Shropshire) [SSS]
Visitor Radio for Bath [VBA]
Visitor Radio for Hastings [VHS]

Irish RTÉ and commercial radio stations containing Radio O in the name:
8Radio.com [8RD]
iRadio (North East) [INE]
iRadio (North West) [INW]
Radio Nova [NOV]