Does a 63a Commando Socket require RCD protection?

Correct. The 63A socket, even for a mobile or transportable unit, which this is, need not be RCD protected at 30mA, indeed it need not be RCD protected at all. However, your proposed time delay RCD at 100mA is entirely sensible.  

more here 
https://professional-electrician.com/technical/the-importance-of-omitting-rcds-in-accordance-with-bs-7671-2018a22022-napit/

or here

https://professional-electrician.com/technical/additional-protection-for-socket-outlets-electrium/

Be aware that this rule about RCD protected sockets has seen a lot of changes in the last decade (in 2018 and before that in 2015 and also before that as well) it may change again but there are plenty of installations out there to previous versions and that can cause issues as to how much changes when things are repaired or when there are different assumptions about what level of protection is in the cabin and what is done in the main building , especially if the unit moves from site to site.

regards Mike

mapj1 said:

indeed it need not be RCD protected at all.

Unless it's on a TT system, where an RCD may be needed for ADS even if not for additional protection.

   - Andy.

mapj1 said:

indeed it need not be RCD protected at all.

Unless it's on a TT system, where an RCD may be needed for ADS even if not for additional protection.

   - Andy.

true - but a delay one may be good enough, and makes sense for discrimination.
To give nested protection, on large outdoor events (think half MW genset) we might have 300mA 1/3 second earth fault relay at the genset (128A or higher in singles) 100ma 1/10 second for the heavy distro (63A and up) and 30mA instant for the small stuff (32A and down) that eventually feeds 16A sockets and lights. An all-out trip is very rare, but still catches any catastrophic faults