Thanks Tim, current update:
had a good look under the hood (2 bty and 24v) and inside (24v fittings).
Volt tested the cig lighter (24v) and towing electrics (24v) so there you go.

Closer look at the phone chager: 12v/24v on the side so guess why that didn't blow...
Not sure about the trailer, need to check the actual trailer lights next.

Who knows about the GPS, hopefully the same 12v/24v charger.

Soooo, guess I need to be careful about running a fridge from the main bty circuit then...