OK that is twin and earth. T&E comes in 2.5 mm2 for 30amp/15amp circuits (sockets and the like) 1.5 mm2 for lighting circuits and the 45amp circuits require 6mm2 or above.



The cable going through the walls to the outbuilding should be sleeved where it is going through the walls and if it's going to be surface mounted you should put it in capping... metal being best. Conduit - the type used in factories