thanks for the suggestions Ian & Bill
I think the 'easy out' method, although feasable, may just leave the caliper a write off if the easy out shears (as so often seems to happen.
i shall be investigating the drill out and helicoil option, seen it done before on calipers, as long as the existing seat isn't damaged by the process it's fine....
local one man band clever engineer is about to be approached

, althoigh i have a pillar drill, i really don't have the means of clamping the caliper square and secure.
standby for the following disaster report ..

yes Bill, icy blasts here but lovely sunny day.... swmbo'd well chuffed... washing dry already !.

pip pip