Paul,
I'd go about a typical Garage or Workshop installation as follows:
  • Install a 25A RCBO at the Main Switchboard in the house, this circuit would be designated as a Sub-Main.
  • Run either a 4mm2 2 Core + Neutral-Screened (Buried Direct) or a 4mm2 2 Core + Earth TPS Cable in Orange PVC Conduit under ground.
  • The cable would feed a Splitter Box in the Garage, which would have a Single Pole Isolator and an MCB for each circuit.
  • Depending upon the type of building construction, the Sub-circuit wiring would be run in conduit in a concrete block/brick building or neatly clipped on the surface in a timber-framed building, with cable protection added where there is a possibility of it being damaged.

Just a small question Paul, how would an overhead cable be run to a shed in the UK?.
I'm thinking thimbles and a Catenary wire, but you guys may have a different way of doing it over there. [Linked Image]
I try and avoid an over-head installation like the plague these days.