Update: electrician arrived, checked the fuse box, categorically said it wasn't the fridge (or any other appliance). We should be getting 240V but whenever a larger appliance is run it drops to 180 - which explains the flickering lights. Contacted Vector and they sent another faults man (different to the last guy), apparently "the neutral at the top of the pole was shorting". Fixed, and everything seems back to normal now.
So now we need to speak to Genesis to see if they are able to re-bill us for the 4 days where the usage was extreme (and not of our doing). I know I probably can't ask Vector for anything as I don't pay them for service.
You didnt mention the flickering lights before....oh well - That would have been a big clue to pointing to where the problem was. Anyway glad you got it sorted out quickly
We thought that was just a power surge relating to more people working from home, as a friend of my wife's who lives a couple of suburbs over had the exact same thing at her place.