<i>To incentivise car owners to plug in, participants in the Octopus trial are being paid a generous sum of 15p per kilowatt hour for the electricity they send to the grid</i><p><i>On the 11th February 2022, the current Octopus Energy fixed 12-month tariff is 37.29p per kWh for electricity</i><p>"generous sum" indeed - they get to sell you electricity at 37.29p to fill up your battery, buy it back for 15p and sell to you again an hour or so later for 37.29p - repeat and rinse overnight and you have infinity pence.
Unless batteries get easier to change in an EV, I am not sure that this is a good idea. It's just gonna put extra cycles on the battery chemistry which is finite to begin with.