Thanks for the help - you've jogged my memory on breather hoses, one of them had split approx. 1 year ago and was replaced. However, that was the opposite problem - tick-over was lumpy and car was almost cutting out going down through the low gears. Have taken the car for a spin today and if I pootle along at around <3000 revs all of my life, there's no problem. Only seems to appear when 'working' the car up at the top half of the rev range. Anyway, will remind local garage of breather hose checks when it goes in on 29 Sep. - apart from Cyd{P} in this thread, the only other shout I've had is that the mass airflow sensor might be on the way out, any views?

Mondeo ST220 petrol - idle speed normally 800 revs, however during quickish use, tick-over speed can vary between 1000 - 1500 revs. Car continues to run @ this tick over rate as if on cruise control so for example, you cannot do 30 mph in 6th gear without constant braking. Temporary solution is to pull over and switch off via the key, re-start and the idle / tick over speed immediately returns to normal.

OK, garage cleaned idle control valve back in Sep 14 and up until this week (5000 miles later) I've had no problems at all. However, I'm now back to the same fault as above. Any ideas what the root cause could be?