It's worth getting up a good working relationship with your local motor factors, i get lower-than-trade on most of my parts now. Just had the same issue with the 205, there were 8 different auxiliary belts listed for the car (of which i needed 3), i ended up trying all of them, guess how many fitted out of the eight? That's right, one. Worked it out between us in the end though, all at no further cost to me. 
You're on the home straight mate, keep at it!

You're on the home straight mate, keep at it!