Shakey

depends, if you are going 16th or 17th

if you are going 17th then your alterations/additions must comply with it

so if the spur cable is buried and nor protected, or/and the socket is not labelled for one specific item of equipment, then yes, its gotta be an RCD

and no, you cant use an SRCD, becuase that wont protect the cable

i have been saying this for a while: even the simplest of jobs under the 17th could result in a board change before the work itself starts