If you are looking for any sand tyres, Witham Specialist Vehicles had some the other day that were ex MOD but unused. Can't remember the make but think they were about £60 each.
No expert on desert driving (or anything actually) but I would take a vice along to assist with any repairs, prehaps mounted on the bumper or somewhere else solid.
Fuses? Track rod end?
Ray Mears recommends setting fire to a tyre if you get into **** in the desert, lets the vultures get there quicker! Sorry, I should say good luck but most of all have fun!