I fitted the Mk3 matrix (GSF part no. 17832B) into my Mk2 and it was a straight fit. It was about £38 I think but just for a laugh I phoned the dealer. He wanted £114 for one!

Needless to say, I got the GSF one.
When I took the original one out, I found it was made by the same company as the one who made the GSF one.
Anyway, heating has been fine but head gasket has just gone!
