After some tinkering and talking, the jeeps system was reset and all fault codes removed.
Its been changing though its gears perfectly again so all was good.
Today I have been out, into drive and clunk, stuck in third again. Into reverse and its jumps into that gear as well.
Now a couple of other issues, with it. With the caravan on all the caravan lights go amiss, but only when hooked up to the jeep. Second issues is as the gear box starts to play up the fan heater stops working. No air blowing at all.
But when the gears were ok the fan was ok.
What the blood hell is going on. Got to tow 350mile home tomorrow!