Garage/Outbuilding electrical installation

I have two garages that are separate buildings from my house. Currently there is a 100A incoming fuse protecting my split load consumer unit. Circuits are divided across the two 80A 30mA RCDs and protected by appropriate individual MCB's. The consumer unit was installed in 2011 and three circuits were installed before the RCD off the main switch, each protected by an MCB. These circuits were 6A - Burglar Alarm, 20A - fridge freezer, 40A - Garage no.1 supply. The garage no.1 had a consumer unit install with a 60A main switch with two circuits coming off of it, 6A MCB - lighting, 16A RCBO - Socket outlets (all circuits in this garage are contained in steel conduit). The supply from the 40A MCB in the main consumer unit to the garage no.1 consumer unit is 10mm SWA 8 metres in length.

In 2017 a second garage was built on a plot of land behind the first garage (an alley way separates the two). A 10mm SWA was run from garage no.1 to garage no.2 a distance of 10 metres between garages. installed in a duct in order to cross the alley way.

Garage no.2 had a consumer unit installed with a 60A main switch, the 10mm SWA supplying the board is daisy chained from the main switch of garage no.1. All circuits from this board are installed in pvc conduit and bench trunking. There is a circuit feeding an outside socket which is protected by a 16A RCBO. All other circuits are protected by MCB's, but all sockets within the garage are RCD socket outlets.


I have two questions;


1. Do i need to install earth electrode and create TT supply at the first garage? i did read that maybe this was not a requirement as the SWA is 10mm 3core and therefore the size of the earth to garages is the same as the earth bonds at the house.


2. Do i need to install more RCD protection? At the house to protect the 10mm SWA feeding both garages? and at both garages after main switches to protect all the circuits? Could i install a 40A 100mA RCD at the house so i get discrimination of the RCD's?