All sorted now thanks Derek
- applied some heat and tried turning it but no luck - then heated lots more and gave it a thump from beneath and very slowly started to get movement upwards - eventually ended up with enough clearance to get a hacksaw blade onto the shank of the bolt and cut the head off it .
Bit of a mystery how this one was so corroded all the others came out easily - guess this one gets the most weathering road spray etc.
Refiited all the new mounts using copper grease on the bolts so hopefully won't have same problem when i do the full subframes re-furb that i have been promising myself