Just a general point. Your eyes are extremely good at compensating for the variation of light intensity over the course of a day. You don't really notice it getting dark until the sun sets. However if you get a light meter and measure the light intensity over the day, you find a huge variation between mid-day and the morning/evening light.Thanks! I imagine in the evenings we'll be doing the same and I'm keen to see how much % of the battery this uses up! I was just curious as to whether the solar panel on it's own will be enough to charge both batteries but I suppose it'll be a wait-and-see kind of thing.
In winter, the sun is low all the time, and it's more or less permanent morning/evening light. And that's without the thick cloud cover that sometimes goes on for days. I have a 4000W solar array on my house, and some winter days it hardly gives enough to charge a phone. You will be surprised at how little charge you get from your solar panels in winter.
In the winter you will need an additional source of charging. A B2B is the favourite, if you move about a lot. You can always go on a campsite to hook up to mains, or maybe find an aire with a low power hookup. Another possibility is to get a cable that connects a Type2 EV charging point to your mains inlet, to charge your batteries up.