Sorry to resurrect a thread from a while ago, but now have a resolution to the problem.
We spent an interesting Saturday doing the cambelt, tensioners and waterpump on my car and, after getting it all back together again, took it for a test run and...... it was even hotter than before..... Sitting above the 100 at tickover and only a low speed fan. Plugged in Tech2 to check it all out and engine/coolant temp sensors gave differing readouts than the guage after reading live data.
As TB pointed out, the guage was lying..... Turns out that the instrument cluster was not 'coded' or similar to the vehicle and possible that it was replaced some time in its history and not set up properly on Tech2. On applying the correct coding the temp dropped an instant 4 degrees plus. Result!!
Car now runs a genuine 93 rising to 97/98 max when stuck in traffic. It took a while to suss out and fix with a couple of electronic keypresses but, thanks to expertise of TB and M_DTM, all is now good. A sincere and heartfelt thanks to both.