I am building another outbuilding to the rear of my home, I do have a garage which is fed by a 6mmsq cable from the CU in the house. the length of cable is approx 18m and is protected by a 65mA RCD in the CU. The new building is set further back and the length of cable from my existing garage to the new building is approx 33m. The purpose of the new build is for my son and his band to practice and record their music, they will have the usual musical instruments and amps. will 6mmsq T&E be ok or will I need to replace the cable rigt to the CU in the house to something heavier and should I use a 30mA RCD in the studio.