So you are paying a surcharge between 07:00 and midnight in order to get cheaper EV charging

To get the true figure per mile, see how much you pay between those hours, adjust the cost to see what it would be on a non-EV tariff and add that to the 10p a mile value

not saying it is not a good deal you are getting, but the cost per mile is being artificially lowered by getting a portion transferred onto the rest of the electrical useage in the house.
Just looked at EON ...
EV vs Non-EV Tariff: EV is 0.27p/kWh more Peak. very little difference (~1%)

. Standing Charge is 8.66p per day more. So the EV recharging true charge is (Peak KWh useage * 0.27p + 8.66/Day) pence more.
(of course, other non-peak and non-EV use will be beneficial, so need to adjust for that the other way, so dishwasher and washing machine use maybe?)