In the best PC tradition I emptied and re-filled the system and heh, what do you know? It seems to be working fine again!
I'll stick it on for a couple of hours this evening to make sure.
Thanks you to all who offered advice.
The heating stays on until the radiators are at what I would consider to be their normal operating temperature, apart from the last one in the system which is still a bit cooler than I would expect.
Once there, it turns itself off and the green light flashes.
Switching the system off or...
Thanks for all your comments.
It's flashing green before all the rads are fully up to temperature, so there doesn't seem to be a blockage in the system.
Where would I check for a block in the boiler?
How do I check for an airlock?
Don't think the heating pipe gets red hot - I'll check.
The...
When I switch the central heating on, it goes on for a while then switches itself off, leaving the power light flashing green,
If I turn the hot water tap on, the system re-sets itself; same if I switch the system off.
However, when I turn the heating back on it switches itself off again...