Seen quite a few posts relating to clunking or banging from the rear end on mk3 hatch and saloon models, common faults are broken springs, strut top mounting failure and anti roll bar bushes and link rods. Not so common faults are rear subframe bushes, wishbone bushes, exhaust hangers, rear bumper seperating from mounting. Hope this helps someone!

 

Cheers, I've got a strange banging too from the back of the estate and buggered if I know what it is, that's something to check

 

The estate model has a slightly different setup for the rear end but same should still apply