I'll save you the trouble, go to Goodwinch (Dave Bowyer) and ask for a back-rack winch platform, £60 IIRC. The you need a decent towball/removable hitch and some cables, or buy the whole bundle including winch ready-made up. I got mine from Donnington for £600 delivered with a loom for each end of the car, isolator, Dynema rope and EPi9 (I think it's that one) so I only need one winch.