consumer unit

I have a garage with an existing consumer unit that has an RCD and existing 32amp MCB\\\'s for a ring main to sockets and a 6amp MCB for lighting circuit. I want to leave an MCB to supply 1 No. external double socket then take a new supply from the CU to pass through a secondary meter and then feed a second CU with a 32amp ring main, 6amp lighting and a supply for an air conditioning unit with a recommended fuse rating of 20amp running at 8amps, starting 8.5amps (inverter driven). My question is what size MCB should i put in the existing CU to feed the meter and new CU? Also what cable size between the 2 CU\\\'s (they will be mounted next to each other.
Any help would be appreciated.

Why do you need the meter? and why isnt the outdoor socket on it? it just seems a waste to have the first CU just for the outdoor socket (which might never be used very often anyway).

The important thing is what cable feeds the first CU and where does it get its power?

And the AC unit is single phase, yes?

Hi Crafty,

Thanx for reply, I want to monitor the usage within the garage only, the outside socket will be used constantly for some outdoor lighting and some fairly 'meaty' pond pumps and filtration systems. If I can I want to keep those separate!

The first CU is fed with what I think is a 10mm SWA from the main incoming supply to the house.

The AC unit is a single phase unit although it may now be a non-inverter (not inverter as stated in original message). Running current is still only 8.2 amps but start current is 49 amps. Again any help would be appreciated. Really like some advise on size of MCB to serve the 2nd CU, and the cable size between the two units.

Many thanks