Revs at idle range from 700-1200rpm

Hi have a 1.6tdi and since I bought it revs at idle have been variable. I originally thought it  was running high (1100rpm) due to being cold and would eventually drop once upto temp or perhaps regen cycle. Car starts at 1100 and normally drops to about 800-900rpm eventually Itakes a while especially when cold) but today the car was warm (90C) and I noticed when in town that the car was slightly accelerating in slow traffic. I was in second gear and it didn't feel right. Checked revs and they were 1200rpm with foot off pedal and the car seemed to want to accelerate by itself. Hit brakes and pressed clutch and it seemed to cure itself and revs dropped to 800rpm Any ideas what the problem might be. No fault codes stored or warning lights on dash. Car runs very well apart from slight wobble at 40mph which I still havent found out why plus a few knocks and clonks etc from I assume drop links/bushes and to top it off a dodgy wheel bearing appeared this week. Going to service and cure clonks/bearing  this week. Winter is hard on cars.

Just worried it will self drive into the back of someone. Where do I start to look? My old 1.9tdi never did this 

Hope the above makes sense

Alasdair