I'd be suggesting to the customer they invest in getting a consultant in to do a proper spec.
It would depend upon the make, but 6mm would be the limit for termination in box and terminalsJust out of curiosity, why SWA for wiring the sockets?
How to you terminate the armour?
If it is 6mm then you will have fun putting 2 of them into each socket.
a 25mm SWA is needed, which obviously inst viable for a few sockets.