Ahh well. I had made a bad memory call. It wasn't the bolt that was stuck. That came out quite easy (word of warning keep a long allen key in the bolt head otherwise it drops inside the swing arm and is a bugger to recover)
Bike up in the air (strapped down on stand)
removed the inner mudguards
block of wood just under rear wheel ready for when it drops
removed top bolt
cracked off the lower nut
tapped bolt through with a narrow drift.
This is when I found it was the sides of the bush that were not moving in the swing arm, the shock was moving on the bush fine.
squirt of plus gas on each side
kettle on, cup of tea
there is space through the bottom of the swing arm to drift against the lower shock eye but i didn't fancy that.
Long thin drift through the lower hole again
taking hold of the top of the shock I swung it hard down against the rear tyre, which after a few 'blows' had it coming free,
once against the drift remove the drift
a carefull swing against the tyre and it was out
Pete