Well, AA met and collected Car for delviery to Garage. Good news from AA man's point of view is that he feels it is NOT HGF as he could not detect any exhaust Gases in the Coolant.
He feels it was Thermostat due to fact that the upper hose pipe was good and warm but the lower one was much/ too cool after the engine had warmed up.
Kaiser Thermostat housing and Stat will be fitted by Garage who will also give it a good looking over and T4.
So fingers Crossed over the next week or so!