jsut called AVS and they said the rubber flange is original vw, so when buying a weber, it comes with a 10mm aluminium spacer that bolts to the original pierburg rubber flange. So the bit you posted jon, was the correct bit.
£30 delivered. Cheers guys, will let you know how i get on. In the meantime im gonna put some electrical tape around the crack and see how it goes, as ive had to miss school today cos i got to the top of the high street and car started spluttering big time, so i had to turn around and limp back to my house. Will let you know how i get on.