Finally got car back from garage today and the news is GOOD! As advised I had a compression test done first and this thankfully showed no problems with the head (phew!).
After that I opted to replace the fan and mounting/housing entirely as I didn't trust it any more. Parts came to just over £100 but well worth it (original VAG). This allowed the car to be run fully for prolonged periods and get the heat up.
Coolant was changed and topped and the car run at speed and low speeds for well over an hour and all was well with the old girl. All in all I was very lucky to get away with not blowing the HG and I can only put this down to good fortune and spotting the early signs allowing me to stop before more damage done.
As in my original post I would advise all to routinely check their fuses and the actual condition of the fan and mounting.....it was corrosion on the bracket that caused the fan to jam, blow the fuse, and the car to then overheat. Very hard to spot if you do a lot of fast motorway type driving where the engine is cooled 'naturally'.
I'm sure it seems like common sense and I don't want to preach to the converted....but it's an oversight I made and could have been costly.
Once again, thanks to all who took time to post with advice.....it is very much appreciated and makes me glad to be a VW owner and part of this great forum
Now that this car is sold I am sure I will have a lot more to post regarding my restoration 16v - the one I expected to cost me money!!!!
Take care all and happy dubbing ;-)
Duncan
1990 Mk2 16v - Royal Blue Metallic