same problem with mine, if u can't get a diagnostics huck up try paper clip test u can find a link on the web which will tell u how 2 do it.

what does it do before light comes on?

Engine managment light, get it put on a diagnostic pod and that will find the problem. My mate used to have a similar problem, it ended up being oxygen in the exhaust system (but your problem could be anything).

when im driving (mainly on the motorway but sometimes in town) the car seems to cut on for about 10seconds i.e. i cant accelerate any more. the orange warning light comes on for a few seconds aswell.

any ideas what it is or how to fix it?

thanks