Hi all. My 16v (5 speed manual) is back on the road having had the gearbox reconditioned at great cost

, and also a new clutch.
We replaced the rear flex disc whilst doing it.
Unfortunately, I still have some drivetrain shunt and banging. If you don't know what I mean by this, imagine getting in a crap old car, with someone going full-throttle then immediately off throttle then full throttle then off throttle repeatedly - the car clunks back and forth, making banging noises as it does so. You don't usually get this much on a Mercedes. My 1986 190E doesn't do it at all (though it is an auto).
But my 16v does quite badly. Even if I don't match revs perfectly on a gearchange, the car can shunt backwards and forwards as you go into the next gear. Or if you make a fast gearchange, it doesn't engage smoothly like it should, but jerks and bangs. Also, if at low revs (1000rpm) it sometimes does the same. I think there is some serious slack/looseness in the drivetrain, but someone suggested it could be the rear suspension.
I was really sure this would go away with the gearbox being done

. The original reason for having the gearbox done was due to a noisy whining gearbox when my foot is off the clutch. Unfortunately the whine is still there too, although less than before. Help please!
Russell