Thanks for the advice fellas...
I think lady luck was on my side for this one - it was late last night and I was having a few beers trying to figure out how I could get round this problem when...I managed to catch a rough bit of the screw with the callous on my fingertip and raise it enough to twist with my finger nails then grab it with pliers and unscrew it !?!?!?!?
It was just before I went to bed last night, cos the beers and all, I thought it'd been a dream....... but sure enough the screw was gone when I woke this morning.
Otherwise I would've dropped it off to a luthier like you said - didnt fancy my chances of success getting mediaeval on its ass with dremels blowtorches etc. My woodworking skills are similar to that of Homer S. Would've probably ended up with a mandolin.