Running 2 supply circuits to a garage

I want to run two circuits out to a garage.
I want to have a lighting circuit and a couple of sockets.
I've buried some 4 core armoured cable at about 750mm and marked it with caution tape just above. I plan to install a small consumer unit in the house with a 40A RCD, 6A MCB & 16A MCB.
My question is how should I connect a pigtail from the meter to this additional consumer unit and should I use the armour as earth and have 2 neutral lines or use one of the conductors as earth and have only one neutral line??

you can not connect your new consumers unit to the existing tails as only your electricty supplier can do this.

Yous should also only use the wire armour for earth as when you use the correct glands it will earth it for you, but the electric co. will want to test it themselves