Not as hard to implement as you might think. https://europa.eu/youreurope/citizens/travel/security-and-emergencies/emergency-assistance-vehicles-ecall/index_en.htm
New EU cars since 2018 already require the technology to be present to communicate without your permission, providing location to emergency services in the event of a serious accident. So they don't have to invent very much! If the phone/data link is already present, the location sensing is already present, and the onboard computer already calls for help if it detects a crash, how hard would it really be to introduce legislation that requires manufacturers to alter that code to record the vehicle location and speed every few seconds and send that data to - say- HMRC to have your charges (and speeding fines) collected by PAYE from your wages, pension, or benefits?
Also the GPS co-ords and time wouldn't take much space on a memory chip, so there would be no requirement to have an always on data connection. If you go out of range, fine, it'd dump all the data next time it made contact. You might not have phone signal at some points in your journey, but it'd be unlikely you'd have no signal at all unless you were cheating the system by knobbling the transmission. Signal loss could be recorded and that data passed back on next contact so dead areas could be filled in.
There are however some things which might mitigate against a lot of extra duty being required. Firstly EV's would still pay VAT on the electricity consumed whether at home (unless you have home solar of course) or a public charger, so there would still be some vat revenue. Granted not much if you can home charge and can get a special low price for overnight charging, but that won't apply to around 60% I believe, of car users who won't be able to home charge. Secondly as renewables bring down electricity costs the vat on it could be raised without impacting peoples pockets, they just wouldn't get the reduction. Thirdly the reduction in vehicle pollution is expected to save the NHS billions in treatment costs.
I do expect however the government will find some way to still charge road users, a) Because they have a massive COVID debt to pay off, b) because it would force people onto more environmentally friendly public transport, c) Because they'll want to tax the peasants off the roads to leave them free for their party contributor billionaire cronies. I'll leave it to you to decide which one depending on your political inclinations.