After about a month in the garage i finally have my B4 back.
Its now the proud owner of a new rear tyre ( Conti avenue !! Any good ? ) and a welded on front sprocket. The mechanic got me a new one, hence the delay, and electro plated it into position, he assures me it is all fine, and up to now it feels really good, although obviously i havent given it too much beans as the rear tyre has only done 55 miles.
The old girl lives to fight another summer