Hi Nicola,
There isn't always a car to caravan switch - our 2000 Elddis Cyclone doesn't have one.
It should still charge the battery when you're towing as well as when you are hooked up.
You should be able to tell from the battery voltmeter whether the battery is charging or not - anything over about 12.8V is charging, and it should be up around 14V.
Did it used to charge or was this your first trip?
Our battery charger is in the seat box, attached to the battery box. I think there may be a switch on it to switch it on and off (but I really don't know for sure, I just think I may have read it somewhere! Though, why you'd want to switch it off is anyone's guess!)
Presumably you were getting mains voltage for your fridge as that will only work on 12V when you're towing and the engine's running.
You might also check that everything's switch on in the 12V and 240V circuits and all the fuses are intact.
I'm trying to write everything I can think of but we've only been caravanning about 6 months and haven't had this problem!
Hope these vague ramblings of another amateur go some way towards helping you!!