DIY Fitting Gas Combi (condensing?) Boiler

That's semantics, but I think if you found yourself in a court of law suing an insurance company who were refusing to pay out, I don't fancy your chances if you tried to claim that you, a self-proclaimed "competent" d-i-y'er, was the same thing as what the insurance company define as a "suitable-qualified workman"?

David

Has an insurance company ever refused to pay a claim due to faulty DIY gas work? Or indeed cowboy gas fitters which are *far* more common?

In some respects you may be right. But if the DIYer can produce a folder of material which covers the installation of a boiler then I doubt there would be an issue that he wasn't competent through doing his homework etc.

In practice, apart from of course being totally incompetent, there would have to be a secondary fault in the boiler for serious consequential damage.