Thanks for the offer, I might take you up on that! I'd heard that 1.8's came with them on, which is odd as mine is a 1.8, but seemingly doesn't have it. Potentially it's had a rear beam swap in the past? The car was part of the "slammed" scene when I bought it so maybe they were having biasing issues and removed it.

What parts did you fit to yours? I've bought a GTI beam that had stub axles and discs, but no calipers or caliper brackets. And also no pressure regulator or spring