As already said, you need a smart meter. I am a sub 10k miles user.
Personally, I use Octopus Tracker and the average rate is well below 20p/kWh and that is okay for me. In the last year you could count on one hand how many times it went over 20p but never above 25p so far this last year. A 20p fill up of 50kW is £10 and that would easily last about 150 miles this time of year, usually much more in summer.
Clearly you have a few choices to make – which did you go for in the end?
Skoda Enyaq Race Blue