Are you sure it was British Gas?

This seems very strange to me and I'm wondering if it was a scam like the Sky warrantee one's. I think they just wanted your bank account details just as you get spam emails. I would be very careful indeed and NEVER give bank details over the phone unless you know exactly who you are talking to. In this case I would always ring back the accounts department before parting with any information in order to verify the call. The fact that you say they were rude rings alarm bells for me. I've been with British Gas for years and have never found them to be rude or even unhelpful. I have had calls from the security department from my credit card company when my card was used unlawfully. I always tell them I will ring them back. If they are who they say they are, then they will understand the reasons for your caution. My advice for what it's worth is ignore the call, don't let it upset you and put it down to experience.

Just a thought.

Elaine