Why do all the outlets freeze up and stop working at the car park?

what do you mean by "freezing up"? if the outlets are literally covered in ice or condensation, that's a humidity and temperature fluctuation issue - in an unheated room the metal cools down and collects moisture, which can damage the contacts or cause a short circuit that trips the protection. but if they just don't work in the cold, then it's either the main circuit breaker (it might be switching off on a timer) or the RCD and breakers are reacting to current leaks, which happen more often in damp conditions.