Gamer, sounds quite like it could be coils (or plugs if the bike runs rich). I assume the gsx600f (the teapot!!) is wasted -spark? Might be worth running a multimeter over the coils and checking the impedances. Also a visual check of leads for damage and in the dark for arcing and corona.

Im in Bristol also so if you want me to pop over, no problem.

merv

btw i have a new coil somewhere, so substitution could be tried.