Thanks all...Yes turned out it was turned up to max and that is why it was (obviously !)overheating.
Very little can go wrong with these very old and simple boilers as the only things that can break are the thermostat and or gas valve or so I was told
No sign of Carbon monoxide leak...
Morning
I have an old floorstanding Potterton Kingfisher which is in the cellar.
When I went downstairs the C02 alarm was going off and the cellar was like a Sauna.
The central heating had been on for about half an hour.
It is usually warm in there but never that hot.
Anyone any...