I've just seen a reply ..

Oh, good grief, I've just found it - from "Aioe News"; I wasn't looking for that !!

Well, I feel foolish, but grateful for ALL the replies which I have now read using the link to Google Groups. I didn't realise the boiler had two separate and isolated heat exchangers so that the heating and water were different circuits. A moment's thought, of course, would uncover the reason why, but clearly I wasn't thinking !!

The responder who said I was right to get a Plumber in was obviously spot on with his reply. All I can do is plead old age and brain fade. Thanks for all replies.

Mike.

Yup I guess that would throw you if you were looking for a different name ;-)

The two heat exchanges bit would apply if the boiler was a combi. However since you mention the question about "why doesn't the hot water come out of the taps at the same rate as the cold does?", it sounds like you may have a "system" boiler (like a heating only one but with the pump and various other bits built in) or a "heating only" boiler with a separate cylinder for hot water?

If the latter, then your hot water is still likely gravity fed even if the heating system itself is sealed. There is a second heat exchange with a cylinder as well - however its built into the cylinder.

Yeah well some folks have no sense of adventure ;-)