Just been on the JEEP Club web-site, recommended by bother-in-law.
On it there's details of an interesting site posted.
www.anglegrinderman.comIt's a guide to the removal of a wheel-clamp, the legal & moral implications of doing so, and general information about what to do if you're clamped.
Sorry the first sentance should have read brother-in-law, but it sounds better.