I am with ovo as it suits me better, I get 6.8p a kw just for the car (they control the ohme charger) when ever grid is low to medium (you get slots) but they will still charge you in the last hour even if grid goes high as they have commited to that time slot.
it is also a addon and not a tarrif so you can go on any of their tarrifs you want.
works out fine for me, I also get £10 credit every month for powermove and keeping use low during peak times.