Heya, just an update.

the other day i had my heating on full heat, when driving all of a sudden it went very cold, i checked the engine heat and it was just under red, i stopped on the side of the road and checked the water in the coolant bottle was bubbling a lot.

It was on the max level maybe a little bit under in the coolant bottle.

i dont know anything about cars but i did have some bottled still water in the boot and put some in, a little over the max mark, the engine heat stayed in the middle, rising a little but not going up to the red.

Could be that your head gasket is already leaking or that the thermostat is not fully opening.