Thanks for the replies - much appreciated.
Well, I think it is the right part (18 10 2 208 788 ). That tallies with the realoem link that doughboy kindly sent through:
But presumably the centre silencer in the diagram (part no2) is different to what I have?
So I need to either a) get that part (if possible, doesn't look like it has a separate part number), b) get my existing modified / welded, or c) have a part made up (not sure if that would be £££).
These things are never as easy as you imagine!