Vauxhall Cavalier L reg 1.8i - losing power?

Hi for about the last 2 weeks my car has been running quite lumpy. It loses power, then kind of 'spurts' forward as I am driving, and feels like it is going to cut out.
It did cut out once and the engine management light came on. It restarted so I got it back on my drive, the RAC couldnt find anything wrong with it and it ran OK when the guy was here.
I have changed the air filter - any other suggestions?

Cheers, Kez