Thanks for the replies, I know its stupid to ask after I pushed the button, but I have had absolutley fantastic service from British Gas with a homecare plan I took out, it seems most of the system had just about had it, and everything has been replaced without grumble, with fitters that all know there stuff, polite and turn up when they are supposed to, so it just made sense for me to stick with them.
In the last year I have had 2 new fans for the boiler, a new hot water tank, a new imersion heater and a 2 way valve (the motorised thingy)
On paper I should save about 16% but I suspect that I might just save a bit more as my bills had been out of control & think the old boiler may be an under acheiver.