I can confirm replacing the lower main shaft bearing has cured the whine and upon inspection is the only bearing with severe wear as described from all the Vauxhall threads. The gearbox is now very quite but 3rd and 4th still vibrate slightly when your hand is on the gearstick, which is fine for now until I can be bothered to do the other bearings. The gearbox no longer throws the gearstick backwards when you lift the clutch up in first gear and the slack has been taken out of the throw of the gearstick. Bit of a 'mare of a job but you only have to take the battery and battery tray out, gearbox mount off and then release all the nuts securing the gearbox end cap to the bell housing. Dropping the engine slightly makes access a lot easier.
Remove the circlip from the bearing and using a puller, pull 6th gear out a good 10 mill which in turn forces the bearing towards the end of the shaft. Then slide the 6th gear back to its original position and use the puller on the bearing itself. (This did require a bit of heat to get it to come off)
Push the new bearing on with the puller (used in reverse) refit the circlip. refit and fill with gearbox oil.
Job Done.
Just make sure 6th is on its synchro properly.
£47 repair v £1000 recon box