Thanks guys for all the replies. It is an issue I will be taking up with the builder. I have checked next doors and theirs is the same. Makes you wonder what other non compliances exist on the development. I have ascertained that the single socket is not a radial; it isolates off the upstairs ring breaker.
Just another example of poor workmanship. We have had an exceptionally long snagging list. Some of it, like upstairs sashes fouling on the brickwork when opened, blockwork in the garage bowing out and a front door warped and the frame not plumb, I don't class as snagging. What happened to attention to detail and taking pride in the work that you do.