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As said I think you need to check the coolant is actually circulating in the system,if it’s not then no hot coolant will be passing the thermo fan switch in the radiator you will just have heat sink along coolant hoses.so the fan will never usually kick in,also if the interior heater works at idle ok but goes cold at raised revs this would also indicated lack of flow,as the internal fan is cooling the coolant sat in the heater core and taking all the heat out .
Check the flow back to the expansion tank at raised idle it should be quite fast through the small hose.
Hope you get a fix soon.

Thanks again for the replies.
Spent a few hours on the car today.
Tried new thermo switch.... Still no fans coming on.
Checked both switches by applying heat to switch whilst plugged into fan and fans work, therefore must be a blockage of some sort so the thermo switch doesn't get hot coolant on it. I tried rad flush a few weeks ago, so I'll try to see what the flow is like back to the expansion tank, possibly a faulty/broken water pump.
Thanks again for the help.

Finally sorted.
The return metal pipe that runs across the top of the head was completely blocked, I tried to unblock with acid, coat hanger but well and truly blocked. In the end used some 10mm copper tube in its place. Not pretty but does the job.
Once again thanks for your help.

Good result, I'm not sure that I remember any steel piping on these car's cooling system - "function before form" works in my world!

Edit:- sounds like that poor car has been living with no corrosion protection in its coolant, never a good idea.

Steel pipe runs above the head, under the plastic cover on the return from the rad. Probably a mix of corrosion and some sort of rad sealant, certainly nothing getting past it.

Vanilla cup wrote: Fri Mar 01, 2019 5:53 pm Steel pipe runs above the head, under the plastic cover on the return from the rad. Probably a mix of corrosion and some sort of rad sealant, certainly nothing getting past it.

I know that Mk4 Golfs at least had waterpumps with plastic impellers that could break up. I’d take the waterpump out & check it.

I’d hope by now everyone had replaced their cam belts and their water pumps.