Nothing in haynes that can
help you there mate, the only note in removal and refitting rear disc is
15. slacken and remove the rear hub nut, then slide off the toothed washer and remove the outer bearing from the centre of the disc.
in abs section it is really helpful and reads:
Rear reluctor rings
21. The rear reluctor rings are pressed onto the inside of the rear drum/disc. If removal is necessary, remove the drum/disc and take it to a seat dealer, who will have access to the necessary tools required to extract the old ringand press on the new one.
Good ol' haynes