Awww Mel, what a horrid situation to be in.
They are usless because due to a serious error at the Passport Office, I have 2 passports!! I lost mine and only realised a week before I was going on holiday, so I phoned them up and asked if I could go down, so I went to Liverpool on the Monday to take all my forms etc.. and returned on Friday to pick it up. No problems, anyway I went on holiday and when I returned I had a package from the Passport agency - a 2nd Passport!!
I phoned them up to tell them and they just said "oh its fine, you can use it in an emergency" (I did feel better though when I went to live in Cyprus as my Mum kept one of them just incase!)
Your situation is very baffling, I have had my name changed by deed poll and that caused no problems aswell. So with all the ID you have sent them I can't understand what the problem is, have they actually said that they don't think you are who you are.
The only things I could suggest is, as Mez said turn up at the passport office and stamp your feet until you get to see someone senior, or go to see Greg Pope personally and see what he suggests. You might not get anywhere with that one, but at least you have tried. What about getting in touch with a newspaper??