Ok folk, I appreciate all the info for now.

Bit more though... the cable has an earth wire, my mistake. Until I get a day off to get it done properly, I have literally popped the cable two inches under the grass. It is nowhere near any drains or somewhere that work is likely to take place, and is not going to get in the way of cutting the grass.

The external electrical box on the house has a trip switch too.

I hope to get some armoured cable in the next month or so, but would prefer to still leave it as a temporary installation a few inches under the ground as I know that no work will be done that could affect it. It is just the fridge running off it as any garden tools are powered from another extension plugged into the kitchen.