^^This^^
There's been a number of threads all with similar queries recently.
Put the inverter in ECO (use the portal, not the app!) then set a Timed Charge for the IO period (23:30 to 05:30) and set the SoC % that you want to exit the off-peak period at.
I'm on IO and thats what I do. The only thing that you have to watch for is if the IO app schedules a charging period outside the "normal" times and the car starts charging in those times. In that case then the house battery will be used to meet some of the car charging load. This is less of an issue if the charging starts before the normal 23:30 off peak as the Timed Charge setting will still charge the battery to the required SoC%. If, however, the car charging period runs on after the normal off-peak time ends you may find that the battery gets dumped into the car leaving you with a reduced amount for daytime use.
To get round this you can manually change the Timed Charge period to match the IO times. Be sure to change it back though otherwise you might find the battery charging in peak times.
Personally I find that the 6 hour off-peak "standard" times are plenty to charge my Model 3 without needing to go outside these times.