The socket would not be part of the ring only the switch. It is common to us a RCD FCU for this job as they then also fuse the outside socket.
Today of course with all sockets being RCD protected only a FCU would be required.
Using a grid switch which is able to take 20A not the 6A of lighting circuit would also be an option and fuses are available for these but the standard FCU (Fuse connection unit) would be cheaper method.
It would be normal to switch both live conductors line and neutral and the FCU with and without RCD combined do switch both live wires.
However it is very unusual to have outdoor sockets as part of a ring circuit,
how many are there, are you sure they are in the ring?
Also don't forget outdoor wiring is covered by building regs. part-p before attenpting any DIY alterarions.
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