ohme cable with type 2 or commando plug are 32amp rated. They also do a granny lead....
Have a chat with the landlord over fitting either commando or even a dumb type 2 charger. It will help future residents who live there.
octopus hasn't got anything as close in rates to that, apart from Go's four hours (5p) but the other 20 hours is at 14.02p. Also standing fee is 25p per day. If you can shift your needs into the the cheap period, you can get the average below your current rate. Or you can play Agile roulette game, but this requires a lot of effort to get an average cost in single figures.
Other option is get an octopus customer to buy the lead, and buy it off them.