Went down to my local friendly dealer today and got a new wheel arch liner (1K0805978B) and a collection of screws (N10354602) and rivets (N90833801)
Liner was £18.03, screws £2.16/8 and the rivets were £2.88/8 All +VAT
£27.69 all in.
I just need to get some Loctite so nothing falls off again