Everyone is different – different mileage, different cars. Some cars like Kia are not compatible with OVO and Octopus as they are on Intelligent Octopus (IO) – but there are reports of 12v batteries still being flattened by repeated polling of the cars status.
For me, IO is cheaper, not least because OVO won’t work with my Kia. My overall annual use is 8300kw, about 3500kw of which is EV charging, so I’d save a minimum of £900 a year, even with the higher peak day rate. Even more if I shift things over to off-peak use.
However, as others have said, the market will undergo a lot of changes once the price cap ends, predicted falls of 20% are being mentioned for July, so might be worth waiting to see where it all goes.
In life, it's not who you know that's important, it's how your wife found out.