1999 Vauxhall Vectra engine cuts out

The Problem

Hi. I was just wondering if anyone can identify with a problem I'm having with my car. It's a 1999 vauxhall vectra 2.0, and the problem seems to be that the battery light and engine light come on and the engine cuts out when the car is slowing down or coming to a stop. This happens all of the time recently and am beginning to worry that it could be a major problem. The car is fine going at speed until I have to slow down, go down a hill or turn corners when changing down gears. Examples include in a town or traffic lights, roundabouts, etc... when you need to change gear and slow down the engine cuts out and car stops.
I have checked the oil levels...all ok
The rev counter when car first starts hovvers around the 1 mark but after driving for a while it starts to drop. Then the engine starts to cut out.
The car starts ok, runs ok, but just keeps cutting out all the time after driving around 10 miles or so.
Can anyone help me at all???

Thanks in advance

Steve