Edit....... just realised you said Mazda. Not sure if that's compatible on Octopus IOG. Might need a wall charger then, but that's quite the wasted outlay for a PHEV.
Just use the granny charger, it's all you need for a PHEV. It's what I use for our X5 45e (21.4kWh).
Get on Octopus Intelligent Go tariff (IOG). You get 7p/kWh between 23.30 and 05.30. But you can use the app to choose "departure time" for a full battery and use the system to give you extra charging slots as you see fit during other times of the day. You can then do all your washing/tumble drying/dishwasher etc at 7p/kWh.
For example, if you say need to charge up from 50%-100%, then don't plug it in overnight. Turn on your 3pin plug at say 7am, select departure time in the Octopus app for 11am, then it'll give you a charge window from 7-11am.
On the other side, if you have a battery that's flat, then around lunchtime plug your car in and select departure time of 4am in the app. It'll charge overnight, but will also likely give you charging sessions throughout the afternoon and evening, further allowing you to use the 7p/kWh rate during your high usage times.
For a further bonus, drop charging speed in the car to say 6 Amps and enjoy even more cheap sessions for all you electric usage needs. This game could land you in trouble with Octopus if you have a large battery EV and are always trying to charge at the cheap rate