today's follow up - managed to get in touch with previous owner and they confirmed that they had same problem and had done most of the work I have had done to no avail (wish I had known this sooner)! They said last thing they were going to have done was replace the "clocks" but in the end it was causing too much stress so they traded it in. They had also taken it to Ford and no fault was showing on their diagnostics (same as me). Had also taken it to various garages and they were baffled.

Before getting in touch with them today I let car idle and get up to temperature which is around 94C and will happily idle at this forever with ALL hoses including bottm hose HOT, then took it out for a drive and car onboard diagnostics showed overheat up to 113C so stopped car, gauge went down to 108C, lifted bonnet and bottom hose COLD, when I got back ino car literally seconds later, gauge was showing 98C. Drove back home - total round trip of 1.5 miles and let car go back down to idle temperature of 94C, felt bottom hose which was now HOT again and supposed coolant circulating again???