Thanks Architex, ECP seem to have doubled the price, maybe they are about to do a up to 50% off everything sale?
I managed to cut the lid off this thing and found it had cracked in what is the usual place. That may be the problem, it also had signs of rust and water ingress. I have washed the thing in brake cleaner and petrol until it ran clear. I can't see anything else wrong with it. there is no clutch. My current theory is that the swash plate assembly was able to pop past it's stops and the T45 spline drive was popping out of the brake caliper.
I can't see how the belt could slip or these cogs slip and the wobble-plate cogs/swash plate seem to tight and not damaged.
I intend on greasing it, fixing the plastic and maybe shimming or bushing out any slop and try again.
Looking on google, this is a common problem on VWs which is the same design but not an identical part and there are a few Passat threads about fixing them.
https://dl.dropboxusercontent.com/u/...5/IMG_3179.mp4