Just a follow up incase anyone else has the same or similar problem. I found and fixed the fault yesturday, although it did take me nearly all day After spending most of the day checking every bit of the engine I could think of and talking to any mechanic friends I could think of, one of them suggested trying to drive the car however slowy it may go, to see if it refound it's settings. Why not give it a go thinks me, Iv'e tried everything else. (I hadn't tried to drive it up until then as I didnt want to cause any further damage) It was then I realised it wasnt actually going into gear, the stick moved the dash display moved but I couldn't feel any take-up by the box. This got me thinking, the engine wasn't the problem, the engine was in major Limp mode. (Nice of it to tell me) I checked to autobox using the vcds and sure enough there was a fault stored. The fault related to a blown fuse, (id checked as many fuses as I could find) more hunting thru manuals showed the fuse lives next to the engine ecu and supplies the gearbox ecm. Tried a new fuse and it blowed straight off. So that got me thinking about changing the battery(thats when the trouble started) further inspection, and I found some damage to the main harness that runs along the fire wall, past the battery. I had, carefully lifted the loom out of the way when I removed the battery but a previous owner obviously hadn't. There was a messy repair in the loom, which had been neatly hidden and I had upset when moving it. Two wires soldered and heat shinked later, fuse replaced, fault cleared. Car back to normal
The main point to make here is that the engine was in Limp, major limp, restricting the revs to a little more than 1000 rpm popping, banging in the manifold if you tried to rev past that, BUT no fault codes in the engine ecu, no check light on dash, all live engine readings seemed normal. Lucky I had something to read the autobox faults or I think I would still be there now.
So car now runs lovely on petrol and autogas, took me all day, but could of been a lot worse.