Mongoose/magnex are probably the most commonly used stainless systems for the Mk1, if you haven't already sourced one then its worth taking a spin out to Paffs Mk1 aladdins cave in Caerleon...he'll be able to help you out!

Is your car the one thats on autotrader? G616 G?G or something like that?? I only ask, as I remember seeing the mileage & the fact that its only 10miles from me. I was gonna have a look but TBH I just dont have the room for another