Thank you everyone for your replies.
I'm still debating as to whether an electric car is worth it for me in the first place but, depending on the deals and types available, I might just bite.
There are some calculations on running costs in the Are converting to electric cars realistic thread. but gist of it follows.
Exact fuel costs depend on driving style, car, outside temperature, but in general terms is petrol cars get about 400-450 miles to a tank, which is about £60-80 to fill (depending on location and car)
Most electric cars have official range of around 220-260 miles (say 185-230 miles typically), so 2 charges gives similar range to tank full of petrol. (For completeness there are also longer range cars that do 300+ miles, conversely also city cars with less range)
Typical electric car costs £6.50-7 on overnight domestic electricity to go same distance as tank full of fuel (2 overnight charges of £3 to £3.50 each). So overnight electricity is around eleventh of price of petrol
However those using public chargers will only save about 30% vs petrol (if they are registered with app or charger card). But will pay similar amount to fuel if using normal public chargers at turn up and pay rates, and around +10-15% if using expensive rapid chargers priced around 80p /kw
Assume installation of home charger is £1000 (as a one off payment), might be contribution for some new cars. (takes about 8000 miles of cheap electricity saving to offset this cost)
An electric car owner doing about 10,000 miles per year, charging at home, saves about £1300 per year (say £100-110 per month). Typically also saves £150-200 each time on servicing as no engine or oil changes etc. Against these savings car insurance costs bit more
For new cars there are currently massive savings if you search (try carwow etc). As an example a CUPRA Born, gets £7000 off for PCP, another £1500 for Government grant, and a seasonal £1000 off til end of September, and wall box (home charger) for just £99 (saving about 900) so around 30% off the (arbitrary) list price