This is 100% my boiler, rob884.
Sorry if I didn't make things clear. I'm an amateur at all this, as you can no doubt tell.
The boiler was working, was then moved into the garage and the DHW did not work thereafter. I had had a similar problem with the CH diverter pin previously and so cleaned the pin on the DHW valve differential. The part snapped, so I replaced it, assuming that this was the problem.
Since then, I have begun to suspect (because of the symptom mentioned above) that - somehow - the DHW hot and cold pipes have been crossed, resulting in no DHW. CH is fine, by the way.
Thanks for your comments, Paul. I hope you're wrong. When the boiler was serviced by a CORGI chap a few months ago, he thought it was only 2 - 3 years old and looked good - so I'm clinging on this hope!
The chap who moved the boiler is due back here today, so watch this space. Just hoping that he's made a simple b*alls-up which is readily rectifiable.
Thanks to all.