If you have Octopus Go, there is no reason to set the departure time through the car!
The charge schedule still needs the departure time set for the following morning but, doesn’t need the car to achveive this.
By plugging your car in after 5pm and setting a deparure time prior to 11am the next morning has the benifit of addiditional half hourly off peak slots during on peak hours. In essence your are gaining more cheap rate charging time, than setting a charging time from 12am to 5am departure time.
Ohme isn’t a product I install regularly, as there are better chargers on the market. Unfortunately Ohme along with Octopus and Ovo have you by the the bollards if you want flexible cheaper rates.