Which variant are you thinking of, there were 2 10ton GS cargos, a crew cabbed gun tractor, a Howitzer tractor and a recovery; the recoveries are quite common but the best looking and most desirable is the crew cab.
The mechanics are somewhat Heath Robinson, the portal front axle with bevel gears in the king pins, the steering system and the compressor drive being prime examples. The 3 speed transfer box can develop a self destructing vibration above 30mph and the twin plate clutch will stick together if you leave it parked up for more than a few days.
Spares are difficult to find but the B81 should not be a problem as they were used in other vehicles.
It looks like there will be a recovery in the Wiltshire Land Rovers sale at Melksham in the next few weeks.
Have a read in the Martian section which includes a photo of my 10ton cargo that was disposed of in 1989 for £1400 with just 1200 miles on the clock.
http://hmvf.co.uk/forumvb/showthread.php?8975-Leyland-Martian-Gallery