2001 Vauxhall Corsa overheating massively and dont know why

i had an accident in my corsa a few months ago which broke my radiator on the way home (yes i stupidly attempted to drive it!) it was overheating to the point it boiled. my mate then took it upon himself to throw water on the engine the cylinderhead warped and the car was knakerd.

i had it repaired and had the head skimmed and had it pressure tested all was fine.

now the car is overheating randomly on its own sometimes doesnt even start and the heaters blow out cold air when its set to full heat and highest power so maybe an airlocks causing this? i dont have a clue and seriously considering binning it! any suggestions?!?!?!