A friend at work tells me that it's entirely possible to service your own
gas boiler. He says all you have to do is clean the deposits from the heat
exchanger, and that he's done this himself for the last 15 years on his
current boiler, without it giving him any trouble.

He's got a simple central heating boiler but mine is a combi (a 2-year
old Baxi). Is it still possible to do this? More to the to the point, is
it advisable?

TIA for any advice.