Hi
My combi-boiler has started doing odd things. When I turn on a hot tap it reaches the correct temperature after a few seconds as normal, but then a few seconds later it runs stone cold. Over the course of the next few minutes it gradually warms up and stabilises at a sort of tepid like-warm temperature. Does this sound like a faulty thermostat? Would it be a big job to replace (I'd probably get someone in to do it)?
Ben