If you’ve run a new circuit to supply it, that’s building control signoff required if the spark plugs wasn’t qualified to self sign off.
If you’ve fitted an invented cylinder, that’s needing a G3 qualification for self signoff or building control signoff.
Heat pump itself nothing is needed; and you can’t have MCS union signoff because they don’t actually inspect anything (no installs are properly checked; it’s just the office paperwork they care for) and the union rules are designed to protect union labour by saying that you can only get a certificate if it’s been installed by an MCS union member.
Fantastic. Thank you Marko, that is great, yes, the electrical connection has been signed off & I’m not bothered about MCS atm. Will tackle it in the future if it becomes relevant to what we want to do.
FWIW I think with the number of heat pumps being installed by the speculative developers (Barratt etc al) which are non MCS union labour non MCS installations - just building regs - we should see less focus on those bits of paper.