My mum had a similar issue with proof of identity recently, as she was setting up a new savings account with The Halifax. This did cause a fair degree of frustration for her as well - a frustration borne out of a feeling of impotence and lack of information, more than anything else I think.
When she presented her passport, it was rejected since it had expired, although the photo in the passport was recent enough that it was recognisably her. She does not and has never driven, so does not have a driving licence, and we were kind of stuck. According to her they were not especially helpful in itemising exactly what proofs of identity would be considered acceptable to them, so in the end she presented them with a raft of items - utility bill ( joint names) bank statement, bus pass, expired passport ID and told them to pick which ones they would accept. Still not absolutely sure which of those items they did deem acceptable - I think they were just glad to be rid of her, since her frustration with the system was causing holshiness :)