davew: What does your local authority want you to provide as proof of CO2 emissions? If they are asking for a copy of the V5, surely you can send yours in and tell them the CO2 figure is zero?
I far prefer the French system. You pay your €4.10 for a sticker for life for your windscreen and send a copy of your V5. From the Euro figure they give you a different coloured sticker. If running on LPG, you get the same sticker as a hybrid. Most of the time, it doesn't matter but at times when the air quality falls below a certain level, they restrict what can enter the cities (which usually means a minimum of Euro 6 diesel and Euro 2 petrol), can go in, the older diesels can't. It's an on the spot fine if you enter without the correct, or no, sticker. None of this 'you can drive any old polluting pile of junk into the cities as long as you are prepared to pay the money' like we have here, irrespective of the air quality at the time. The restrictions in France normally only come in during the summer when there is plenty of sunshine and no wind to disperse the pollution, the rest of the time it doesn't affect anyone.
Then again, maybe I'm just biased as I can go anywhere in France (and Germany, Belgium and the Netherlands) at any time but still have to pay my £12.50 on the odd occasion I have to venture inside the M25.