I posted under this heading back in May, and thought I'd post an update.
I finally got my downpipe fitted yesterday, and I think I may have got an original equipment pipe. At least it looks just like the original, with a square shaped bracket which fixes to the gearbox.
Cost was £70 +VAT from T.G. Silencers in Rochdale. The pipe costs £147
+VAT from a Peugeot dealer.
I was really suprised when I saw the bring it to the fitting bay because no one else I tried could track one down (including Kwik Fit).
Anyway, I've rescued a label that was on the pipe, and it says PG473 734J, so if anyone can identify this back to a manufacturer or supplier, I'd be interested to know.
Now that I've finally got that sorted, I'm gonna ask some questions about improving the handling ...