Please excuse a newbie dragging up and old topic, but if you have a look here, I think you'll find what you need:
Land Rover - LOKARI & Industry Representation Hanna
I bought a set of their plastic front wheel arch liners for my old Opel Manta Coupé a few years back and they were absolutely superb. If the Land Rover ones are as good, they'll be a worthwhile purchase. Add some Bilt Hamber Dynax S50 before you fit them and that should hold the rust at bay for a good while.
I hope this is of interest.