Hi Gareth,
There are two different rear bushes for the trailing arms (lower links) as there are two distinct pairs of arms. My understanding is that series one cars had the smaller diameter bushes...563512, whilst series 2 cars had the larger diameter bushes....548595. Now the strange this is, the parts book only lists one pair of arms, which are for the series 2 cars.
You'll need to measure the diameter of the bushes in your arms,...if they are just over 1" then you'll need 563512, whilst if they are 1 7/8", then you'll need 548595.
Ron.