I have just moved into to a house that was built 9 years ago. The house consumer unit has a RCD and one of the breakers covered is the supply to the standalone garage, fed with an armoured cable. The garage has a small consumer unit with a main switch isolator and two breakers. One for sockets and one for the garage lights and existing outside lights. I am in the process of adding additional outside lights and a water feature. Should I fit an additional RCD in the garage consumer unit, or is the one on the house sufficient? The RCD in the house consumer unit is a Legrand one with an 80 amp rating and a 30mA rating. Many thanks.