OK, thought Id post this in case anyone else has the same trouble as I did.
So I needed a new coolant sensor, as my reading was all over the place, didnt want to spend nearly 40 quid for an audi one, so I went to GSF as I heard they were pretty much the same, and it only cost me 16.
First thing I noticed was that it didnt have the clip and seal ring, so I picked them up from audi and set about replacing.
After removing the old one, I compared the two, and noticed the GSF one is fatter and has a longer plunger, didnt think much of it, as I assumed it had been revised to fit better.
But thats when it went wrong. Firstly I couldnt seem to get the new one to fit as flush as the previous, and it would pop out with the smallest amount of force (even when clipped).
Then I took it for a test run, the needle rose and stayed on 90and didnt drop, but then my coolant light came on and steam was billowing out from my bonnet. It had come loose and drained all the coolant.
After cooling down, trying again, even re-fitting the old one, and putting 2 seal rings on, filling up the coolant, it happened again!!!!
I dont know if anyone else has had this problem, but I thought I would post as it doesnt seem as much of a doddle as many say it is.
Could be me, could be a rubbish part. The end result is a trip to audi to fork out 40 quid for a new sensor and a tenner for coolant.
Not very happy