just a thought, and may not fulfil all your requirements, but would an old tractor be suitable. A 3k 4*4 would cause you no end of trouble with running costs, maintenance and so on (tyres alone are likely to be £120 each). If it's only for towing up the track, then a tractor may be a better option, though if you also need it for road driving then not.
disclaimer, I like old tractors, so may be a tad biased.