change of useage

[pjb1]

A customer change the usage of there double garage into two separate areas. one garage has been turned into a gym. The other has remained a garage.
In the garage is a 20A mcb radial feeding 3 double sockets,
6A mcb lighting radial with two lighting pendants
In the gym there are
9x 50w230v downlighters seperate lighting radia feed from al 6A mcb
20A mcb ring main feeding 2 double sockets 2 single sockets.
10A mcb feeding a fcu for an small air conditioner.

This is all feed from a 6 way consumer unit main swich is a 40A/30mA Rccb.
The Cable supplying this unit is a 3 core 6mm Swa. Feed from the main cu via a 32A mcb.

The Tests I'll have to carry out here im not to sure about with a Sub Main.
Dead test to obtain R1+R2 for the sub main supply cable, Insultion test,a Live Polarity test A Ze test at the main consumer unit.

Then moving out to the Garage test the garage and Gym circuits,Continuity Earth & Final Ring, Insulation,Polarity,etc
Live Test PFC&PSCC
Ze
To obtain my Zs is it Zs=Ze(cu1) +Ze(cu2) +R1+R2 for the circuits in the garage

Can you let me know if i've miss anything.

Main Consumer unit is Feed Via a TNCS 100A 1361 supply fuse
25mm Tails 16mm earthing Conductor 10mm Suplementry.