I had problems with one of these Baxi Genesis 80 combi boilers (different issues over a couple of years). None of the CH engineers we called out managed to fix it for much longer than a few days or very low heat, etc. Some even recommended condeming it (rough traders :o)). Last year I had an engineer take a look and he simply pumped up a bellows? (top back is the valve) with a foot pump and it has worked properly ever since. I think he charged me £10.
BTW I believe the Baxi Genesis is a rebadged Chaffoteaux Britonys.
Rob
October 2006