Picture posting is enabled for all :)
Just wanted to say that I was in the same boat as you and wanting a 'proper job' done I gave British Gas a small fortune to do it. It was a disaster and they ended up having to give a large chunk of the money back in compensation. Shop around and don't think that BG are bound to know what they're doing....they subcontract and don't !!!
it might be worth having a look on this website to see if you qualify for a grant towards some of the cost. a work colleague is getting a new boiler installed and has only had to pay a couple of hundred pounds with most of the cost being paid for by a grant:http://www.warmfront.co.uk/do-i-qualify.htm