Quite a few stations had radiolines (Didn't know about Broadland.Cheers for that).However GWR was on a premium rate phone number (the old 0898 ones I think).
The radiolines I recall hearing were
Northsound Radio
Ocean Sound
Downtown Radio (DTR FM)
Hereward Radio (Both Peterborough & Northampton.Northampton was withdrawn when Northants 96 took over.If you know different,let me know).
Devonair Radio
Two Counties Radio
Red Rose Radio
Mercia Sound
Radio Tay (they only had it a little while)
Metro Radio
Radio Tees (I think the plug was pulled shortly after they became TFM)
Signal Radio
The ones quoted above were all began with the area code followed by a four digit code which usually began with 8.
The strange thing about it was that it was done by BT,the stations didn't have much to do with it.(Found that out when I met Laurence Frayne who was Mercias chief engineer at the time).