If you want the arches from a VT model you can get them from several places:
Ebay/Scrapyard or from the for sale section on this site are by far the best places to look
Main citroen dealers are too expensive.
If you just fit the arches they'll look odd on their own, the full kit consists of:
Front bumper
Rear bumper
2 Sideskirts
2 rear arches
2 Front arches
2 Door mouldings
To save yourself some money on respraying obviously hunt around for parts already the same colour as your car, if yours is the red one in the pic im sure these will be easy enough to come by.
In terms of fitting theres a guide in the styling section of how to fit it all.
Heres the link for it...
http://www.saxperience.com/forum/showthread.php?t=55973
If you have any further questions feel free to send me a PM