after this thread, I ended up taking it to a tech locally but it sat there for five weeks and nothing got done (he was backed up with work).
anyway, I ended up taking it back without getting any further with this, but I changed the springs in the trem cavity to four new ones (in place of the three in there before).
it appears to be behaving at the minute, so touch wood its been a cheap fix (£1.00 for the springs)