My brother is getting his garden flagged next week he has a shed down the bottom of it about 20ft away and would like a feed to it so he is going to put it in soon so it cab be buried under the flags with a coil to be left at the shed and coil to be left at the gable end where cu is on other side of the wall ready for a spark to connect ... what size cable does he need and would this be able to be put in conduit or does it have to be armoured cable ......... there will be a fridge in there ,lights and will be using a lawnmower/strimmer