Hi Gavin,
I had a similar problem. Bought a regulator from a local RV Supply for
less than $20. The new regulator was the same as the one sold by my
local VW dealer (he wanted at least $60 for the same part). The
replacement was round in the center and slightly longer than the
original. With some careful bending of the copper tubing and a few cuts
in the original plastic cover, I was able to get it to fit. Be careful
with the copper tubing---it can collapse easily.
Lee Kouns
88 Westy