Unless it is a shiny Series 1 and possibly more so now Series 2 you won't get many people interested in it anyway... and different kinda crooks anyway - defenders are easy to steal, easy to break for parts, fun to joy ride (suposidly) and useful for smash and grab jobs.
A series is too old, slow, confusing, etc. for a standard crook - though - a classic could be stolen to order (a bit like fine art is stolen)
Another simple one for you to do though...
Look at your 3 leavers... 3 leavers - no other vehicle has 3 and it could be confusing to someone who doesn't know what they all do... if say you left them in a sensible combination of positions to disable the vehicle.