This is a bit of red herring. From the POV of the driver of a petrol car, you're paying tax to someone - it doesn't matter who - you're still paying fuel duty. If you don't refuel abroad, you paid all the fuel duty in the UK. If you did refuel abroad, you're not exempt from the fuel duty abroad, you still pay someone for fuel duty even if it's not the UK - so from your point of view, you're still paying roughly the same to someone (taxes on fuel aren't that grossly different between countries a British driver may drive in).

So a mileage tax on electric cars, then you're no worse off than the petrol car driver, you're paying tax to someone, you don't care who is running up the additional cost you have to pay, you're still paying it. If significant miles are driven by UK drivers in France (e.g. a significant imbalance between how much UK drivers drive in France compared to French drivers driving in the UK) then the French and British governments can decide how that gets divvied up after they have received the tax money from their respective drivers without involving the driver themselves. If in reality UK drivers drive in France about as much as French drivers drive in the UK, then really there's no need to worry about it.