I have an update on mine!!!!
Well the cat converter / anti pollution fault reared it's ugly head again. So I decided before I shed out any money for spark plugs (which was my next port of call) I would remove and inspect the post cat lambda sensor. This was really simple to do, just unclip the connection (though mine was a bit mucky) pull the cable down past the engine and through the bottom of the car, and then finally unscrew the sensor from the exhaust pipe.
After removing the sensor I gave it a good clean with just a cloth as it was quite sooted up, gave it a magical blow

and then refitted it back to the car. I was trying to find a serial number for it but there didn't seem to be any ID markings on it at all.
I fired the car up and it's running smoothly. I have been driving to and from work now for a week and it's running perfectly, no erratic idling, responsive acceleration, no poor performance (if anything slightly better) and also it doesn't seem to be drinking petrol anymore. I put £20 in and empty tank on thursday (13.5.10), I've done 93miles and I have a nearly a quarter of a tank left, which is BRILLIANT for this car.
I will keep you all posted on my progress