I have had two radio plays produced by the BBC (radio 4) and currently have two proposals going forward in the next commissioning round (series & and a one off drama). I'm not looking to write something new for your project but would be happy to let you have production copies of mine on CD or script if it would help for timing, structure guidelines etc.
I don't know of any radio production that would be three hours for a drama unless it was a series, the usual for the afternoon play slot is 45 minutes and the weekend slot is an hour.
I thought the links below might be of use:
http://www.bbc.co.uk/radio4/arts/commissioning.shtml
http://www.bbc.co.uk/writersroom/
http://www.dirkmaggs.dswilliams.co.uk/Writing%20Drama%20For%20BBC%20Radio.htm
As writers we are lucky that in Britain there is still a lot of drama produced for radio and it is a good option for scriptwriters looking for a break. The pay isn't bad and you get royalties and repeat fees as well as being paid to attend production. For some reason actors love doing them and you can get big names involved even as a new writer. I believe that the average audience figures for an afternoon play are about 500 000 for a domestic audience on first transmission and the plays are then put out on the internet, digital radio as well as being sold on to an international market.
Good luck, let us know how it goes.
