AIUI from the perspective of complying with current BS7671 there are two issues with using RCD sockets.
1. The standard for RCD sockets was not included in the list of acceptable standards for RCDs in BS7671. There have been claims that this was a mistake, but there has been a big f*ckup in the way standards are written and to the best of my knowlege this has not yet been fixed.
2. Concealed cabling has to be either RCD protected, or installed in specific ways (SWA, MICC, Steel conduit etc) that avoid the need for RCD protection. From what you have said earlier it doesn't sound like your cabling is installed in such a manner.
Aren’t RCD sockets and FCUs back in now? (My books are a few hours away)
I seem to remember they were reintroduced into the online version AHEAD of being in the printed version