OK, So I split the LH calliper, removed the spring (in surprisingly good condition) and the pads. Soaked the treaded end of the pin with plus gas (again), tried molegrips - No joy! Heated exterior of calliper applied mole grips - slight movement? Soaked again in plus gas and left for an hour. Heat and mole grips again, - and - 'snap' the pin sheared about 1/4 inch up from the calliper body! Centre tapped the sheared end and applied small diameter drill bit (hammer action) to see if that would get it turning - Answer no! Another soaking with plus gas and left for tonight. tomorrow I will try putting the remaining pin stub in the vice and try turning the calliper body off (rather than molegrips). Will try with heat also. Once I get this one out (and the calliper rebuilt), I will attempt the right hand one (but I am going to re-use the old pin on this one (just clean it up and leave it in place),