The problem is a 50kWh battery in a car is worth more as a battery than a typical £1500 car.
The lowest end of the market won’t have electric cars unless the batteries are shagged (early Leafs)
And given how insanely cheap petrol is (15p a mile, so £450 for a low mileage runaround) the savings even if electric was free and they weren’t introducing a 3p/mile charge isn’t there.
Battery prices are still falling though, it's just demand is enormous. But I works fully expect China to start having "compatible replacement packs" being built once the volume is there to support it.
A logical future market is battery-refurbished EVs, just a question of where the crossover point is.
A £1500 car is £1500 because it's expected you'll need to replace the engine or transmission pretty soon. That can be up to a £4000 job (£2500 on the low end).
And, as it turns out, a brand new 50kWh battery costs around £4000 to manufacture. Used will be cheaper.