So...
To run a fridge and lights:
Alternatively you could get a DC-DC charger (which would be better) to replace the isolator.
Solar get from Ebay. You can get "scuffed but new" panels for dirt cheap.
I appreciate your Victron desires but why buy an Audi when a Volkswagen will do just fine, especially since the Audi is just a fancy Volks... ? (Don't get me wrong, I know Victron makes great stuff but you can get quality stuff for so much cheaper)
you probably want an AGM battery since that is what they sell the unit to use. flooded batteries require occasional topping up of the water in the battery, which most people don't do.
This one is pretty cheap, is from a reputable brand (though they certainly aren't making it themselves) and is the correct size and type