I have hot water back
Stupid combi boiler with a stupid stupid design. Turns out a seal or something inside the sealed body of central heating pump must has failed and every time the boiler applied mains voltage to the pump it shorted in spectacular fashion.
No problem , just disconnect the pump I thought as I rarely use the central heating anyway. No you can't do that - the central heating circuit is used to cool the domestic hot water (
) and if you leave it for convection to try and circulate the water, it overheats and boils sounding like a brick in a washing machine and then shuts the boiler down blowing the fuses again for good measure.
One of the more expensive fixes (especially as I ordered a premix fan too) but considerably cheaper than a new boiler install.