We have solar panels and a solar battery, in October 2022 we added a SolaX 5.8 triple V2 battery and SolaX 5.0 AC inverter, the battery covers the majority of our need most of the year, in the winter we do import using Octopus Agile averaging around 12 pence @ kWh.
I agree Givenergy have a terrible reputation, if the Tesla installation is only £500 more I would seriously go for it.
Our SolaX installation cost £4,500 however they are now VAT free, adding an addition slave SolaX 5.8 battery would cost us just under £2,000, giving us 11.6 kWh.
Unfortunately I have suffered a brain injury and occasionally I get confused and often say the wrong thing.