Ferger wrote:
Lurked in here for a while (interesting group to read incidentally) so
I know there are lots of CH / plumbing experts around.....

I have a Glow Worm Swift Flow boiler. This afternoon I realised the
radiators were all cooling and subsequently discovered that we had no
hot water from the taps either. Pressure in the CH system is OK and
pilot light was on, so I resigned myself to calling out an expert.
But before I did, I heard the boiler fire up and now all's back to
normal. I hadn't 'done' anything that might have fixed it.... It was
probably 'out' for about an hour.

Anyone got any idea what the problem might be here?

Modern boilers have lots of safety checks built in. Maybe one of them was
triggered?
e.g. flue seemed blocked due to string wind or high level thermocouple
tripped.