Vauxhall Astra '94, waring light stays on?

Yes, sounds like an alternator problem. You will know by now because the battery will have gone flat and the car will have stopped if you've been driving it around, especially if you've used the headlights.
The way to check is to put a volt meter across the battery terminals and look for something like 13volts when the engine is running and 12v when it is not.

Rob Smith
November 2005