The other thing worth considering is do you or don’t you have a smart meter, whether it is Smets 1 or Smets 2 and does a new supplier or tariff call for one.
If you want an EV tariff, its most likely you will need a Smets 2 meter. If you don’t have a smart meter or have a Smets 1 meter you could be stuck on a standard variable tariff waiting for some considerable time for a suitable smart meter to be installed before you can move over to a cheap tariff. @Rene waited around 12 months!