Update: Had the heating engineer round today. He double checked and it was definitely wired up correctly. He checked the boiler and according to him the boiler needs a couple of thermostats - boiler and overrun? Said the boiler is still okay to use as the parts need ordering in. The company said that as they only serviced the boiler in October, they are treating it as if they are still on the job so to supply and fit those parts will cost £116 in total which doesn't seem too terrible to me. Apart from the electronic PCB's that I've fitted myself over the years, they are the only mechanical items I've needed for that boiler in 20 years. Don't know if you need a gas safe engineer to fit them but I don't fancy mucking about with those parts myself. Does what the engineer say seem right? Fair price? Past: FL2 TD4 HSE Auto
Evoque SD4 Dynamic Lux Auto
Present: Audi A3 S Line.

Really depends where the they are fitted, if like some just fitted onto pipe work on the outside of the pipes in the casing, not a problem, though some can be fitted in the combustion chamber, that really is a no, no my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.

All sorted. New thermostats (boiler stat and overheat stat replaced according to invoice). I think he had to strip a few bits off the boiler to fit them - when I looked he was taking the fan out so prob something I couldn't or shouldn't have done myself. I set the boiler temperature up to near max, rads get super, super hot - hotter than they've ever been and after the system has reached temperature if I turn the room stat down the boiler flame goes out but the pump keeps running for a while until things cool down then it switches off.  Past: FL2 TD4 HSE Auto
Evoque SD4 Dynamic Lux Auto
Present: Audi A3 S Line.

My heater super insulated with R4 batts (2 layers of R4 on top) plus building bubble wrap to keep it in place. There is an 80 litre tank under there somewhere! The heater always felt the same as the ambient temperature around 22C (varies roughly 18-25C over the year), but with the additional insulation it is 45C under all the insulation. Heater is set at 65C.
 Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18