I wanted to let owners with similar issues know that I sold my lovely Volvo for a song when I couldn’t get the above problems solved. The person I sold it to (I explained the issues) took a careful look at it and fixed the problem.

It turns out that the air conditioning cooling system fins had been flattened probably at a car wash. It stopped cool air getting to the A/C and the engine itself causing the above problems.

I had previously been advised that the valves needed to be re-bored at significant cost. Anyway, happy that the car got a new lease of life and an inexpensive fix.