I spent an angry 30 minutes on the phone last night to the lender, just repeating constantly 'So what bit of paper actually existed in 1976 that you will accept, so that I can find it?'. Seems they don't know, but want 'something'.
The underwriter is to call my solicitor today apparently, but I've just had enough of the whole thing. I'm not convinced that anybody actually knows what they are doing, as everyone seems to have a different rulebook. There MUST be a procedure for houses with extensions built prior to November 1985, yet nobody seems to have a fookin clue! I agree the council should be able to provide something, but as its not my house its hard getting this information from them - or even if its something they will actually do!