"Hello" and welcome

Couple of things to try and help you ...
Stick your car details and location in your profle .. save you being asked a zillion times !!
Tech help questions are best asked in "General Help" .. more of the forum experts visit there than here.
Overheating of oldish miggys can be loads of things .. from silted up rads to simple things like the header tank cap leaking air (it has a built in valve). many problems are caused by past poor maintenance .. the coolant system MUST have a 50:50 mixture of water:Vx red antifreeze at all times ... not just for the antifreeze ability .. but as an anti-corrosion additive.
I would start by doing a full system flush 5 - 6 times - drain/refill with just water, run for a day with heater on lots, repeat, until only clear water comes out after the run, then refill with 50:50 mix (easy way is to put 5 litres a Vx red in and top up with water !! system holds about 9.5 ltrs water) and see what happens.
The reasson for doing so many, and having the heater on, is you can only drain about 1/2 the system using the rad drain, and there is no engine drain ....
HTH
