I gave it a good going over on the weekend and there seems to be nothing pointing to HG or overheating, the fan is fine, the water level is clear and correct, the oil is fine, driving with the heaters on flat out when the gauge plays up makes no difference to the temperature, and ive noticed a few times its starting to do it when i come to a standstill. i drove it about 7miles in country lanes and it didnt do it, but as soon as i pulled in a mates drive it dropped slowly, i drove off and it came back up. I stopped at another friends and it slowly went down again. I then went home and when reversing onto my drive i notice it start to move slightly again!
will this info shed any more light for anyone?
thanks to all thats helped so far!