Mk 4 astra 1.4 tick over too fast when hot

Hi ive a Mk4 astra and intermittanly it idles too fast, it seems to be ok from cold and when you are cruising on motorway and duel carraigways and stuff and you come to a halt or dip the clutch it all seems fine, but as you sit in stop start traffice it then starts its party trick the rev start to lift and end up between 1000 or 2000 rpm, as soon as the car moves again through air flow it seems ok again, but like i say it seems to be in city type driving its doing it.

The temparature guage reads about 1/3 of the way up when at high speed and just under half at city driving so all seems fine there...

The throttle cable aint sticking or anything and all the pipes to the throttle body and stuff seem ok and clear...

Anyone got any idea's where to start

:icon16:

could be the idle control valve