as above when i reverse or even drive forward on full or nearly full lock, there is a horrible banging/ clunking sound from rear of car, also it feels like it is slightly jumping up, or im reversing over a small rock or brick or something. however on gravel, it just makes one of the rear wheels slip/wheelspin sort of on the gravel, as you can hear it.
any ideas what this could be?

 

If you car is a Type RA or Type R with DCCD then it could be your DCCD is set forward of the Standard setting, it may cause this to happen.

 

Or, if it doesn't have DCCD, then it sounds like the rear or centre diif is in trouble.