Little update!
Cars been with my Dad for a few weeks now, (he had he car for 10 years before passing it on)
Looking like good news, We think changing the rad cap actually fixed the original problem, and because I had over filled the rad when bleeding the system, and then after changing the cap it did legit overflow because it was over full, I thought it wasn’t fixed.
It’s been ran a few times now and it’s not overflowing. The heater in the car is getting hot and cold instantly now!
Car is going to be off the road for a while because it’s got a good bit of maintenance to be done but happy it isn’t anything more serious.
Thought it would be good to post what’s happened Incase anyone else has similar problems !