steve when driving normally do the revs appear to "hang" or take time to return to normal idle (around 850rpm) when clutch is depressed and also coming to a full stop?
In any case it sounds like an "unmetered air" problem. Check your PCV hose (behind intake manifold on 1.6) isn't collapsing. Also check the pipe to your purge/charcoal cannister (long black plastic pipe running across the top and rear of your engine cover from under your throttle body to the cannister on the drivers side firewall).
Heres a code reader/reset tool I invested in. Saves paying a garage £50 just to check a code. Obviously wont be as accurate as the Snap Ons etc for pin pointing fault but for DIY its great. Example is from Amazon but shop around ebay and there cheap as chips!