Thanks for those.. it wasn't so much that I wanted to avoid giving them my details as I'm already in the process of getting a quote and install from them, and don't want to go confusing things
The rule of thumb page isn't one I'd seen before. Based on that, I should have a 5.3kw array + 8.2kwh battery for approx 70% solar use (and rest from off peak)
That roughly tallies with my back of a napkin spreadsheet - when I added the 5kwh N array it gives a total with the 2.6 south of around 5300Kwh per year which is around my estimated usage. And the 8.2kwh battery looked to roughly match with that