uk wiring

hi. here is my current wiring and what i propose to do if correct. i am planning on building a recording studio in an out building. the connection block (diagram 1) after the meter in the house currently has 2 spare connection for more consumer units. in diagram 2 i have shown what i propose to do .connect 2 new units 1 and 2 in the house, and run 2 amoured cables under ground to the out building connecting to 2 more consumer units 1 and 2. one for lights, hvac and sockets. and one for audio equipment. any help and ideas welcome.