It does sound as though your meter is very old, Redkite999 and not up to the task of measuring high currents. The granny charger option may be your best bet but I don’t know what the recharge time would be and whether your likely daily battery mileage could be met.
I’ve heard about smart meters being fitted by area. Not sure how that works. We just got ours done by Avro (Lawri Beck were the installers) but when we enquired about moving to Octopus and getting it installed by them, they said there’d be a long wait.