car just had full service, eratic idle with no power in driving?any ideas???

I'd take it back to whoever serviced it and ask them to fix the probelm, as it looks as if they caused it.

the power problem is ongoing before the service,but the idle has just occured and no warning light on dash,everything checked at garage when i was there but still idle trouble?

What year is it?

Does it have an Engine Management Light?

Does it come on with the ignition and go out when the engine starts?