I used to work for the Beeb but not in the online area. Probably the best thing would be to get someone who works there to invite you into one of the BBC bars
Either the one in Television Centre (Shephards Bush) which has the News centre or the one round the corner from Broadcasting house (its just of Langham Street IIRC).
They're pretty open and I know they let someone working on the Toshiba web site visit the online area and walk around and talk to people. Have you tried getting in touch with them and asking if you can talk to people who work in the online area for a project ?