Is thin site guide relevant to this installation? I don't know as I don't own one, I get along just fine using the actual regulations rather than resorting to the simplified guides.
Ultimately the answer will lie in whether maintainence works are carried out by or under the supervision of suitably competent (or whatever it's called) person(s) or if any Tom dick or Harry may be drilling in to the walls.
Do you have any idea why the other company have quoted for a 100mA RCD?
No don't know why they want to put a 100ma rcd in. It's a TNCS / PME system I thought 100ma was for socket outlets exceeding 32A.