Hmmm. It depends. I've just had a bunch of work done on mine, (235k). Diff mounting bushes, left rear lower track arm, upper right wishbone.... Lower left wishbone bushes.
If you can get under it with the wheels off or the whole thing off the ground, pry the arms with a bar to look for movement, or, if it's cold, wet and you can't be bothered go to a walk in garage tyre franchise type outlet, say you've got a knock from the rear suspension, plead dumb, and they'll a look and advise on what needs replacing. You may have to buy a set of wipers out of it though ;o)
Depending on the worn parts, some you can get from GSF or Eurocarparts (or other fine reputable dealers), some like the track arm are dealer only.
I also took the liberty to replace all necessary bolts and washers as some of mine looked like they'd seen the last ice-age.