We always carry a polarity tester and in the past have only occasionally found a hook up with reversed polarity. But this year we met it an all but two of the sites we stayed on. We found a new installation with EU connections that should have been OK, but it was not. We also found one new box where out of six connections two were OK, one didn't work and three were reversed

. The French didn't seem the slightest worried about it and wondered what all the fuss was about

. I don't know if reversed polarity damages zig units or internal chargers but it can certainly give a nasty shock off a metal hob.
So my advice would be to take a polarity tester and spare leads so that you can cobble together the correct routing.
Enjoy your camping.!!