any ideas on this problem anyone? I overslept for work so had to pace it in the car, got there fine, started the car at the end of the day to hear a rattle coming from the rear of the engine and the revs repeatedly dip below idle speed after a rev which causes it to try and cut out, I've cleaned the throttle body which has helped a bit with the idle, but both problems still persist? 

What engine?

it's a 1.2litre  3 cylinder 

Sounds like cam chain tensioner issues, not unheard of on that engine.