They come separately as far as i know. Not sure of the part number but GSFCARPARTS.COM is a good place for parts, quick, cheap and good quality.

Andy
 
thanks i am new to this car so its a bit hard to get my head round some of the things cheers ants
 
Mine has started doing this over the last 2 days.

The temperature goes as it should to 90 then it fluctuates between 90 and 60 in a rather erratic manner. Going to get it booked in and checked out.
 
mine allready had the green sensor on but i replaced it with a new one £10 off ebay and while i was at it i put a new themostat in now sticks at 90 and no faults on ecu now so it cost me £17 in all bargain
 
So your not sure if the stat or the sender was to blame?

the fault code on the ecu was the temp sender so that was defo faulty i just replaced the stat just in case but now i have no fault codes