You first have to find out why it is stalling when you come to a stop, and that could be that it just needs tuning. I would replace the spark plugs and leads, and clean the throttle body. If you fix that problem you will probably fix the problem you’re having with the battery. It could also be that the battery is old and needs replacing.

Yes, you can use E10.

YOUR problem seems extreme and is one I haven't heard of as a common problem with the Vectra. Ethanol shouldn't really affect the running of your car, as long as the petrol you use has the octane rating it is supposed to have and the ethanol content is no higher than permitted. Generally, there should be no more than 10 per cent ethanol in petrol, but there have been some reports of more than 20 per cent. The biggest problem with ethanol is that it is very corrosive and attacks rubber components, castings and other bits and pieces in the fuel system.