I have seen this interpreted (annoyingly I can't remember where)
as meaning that all ground floor sockets should be RCD protected.

It is not explicitly stated as such. However, I think it is considered
reasonable to assume that downstairs sockets can be used for outside
equipment, unless specific alternative provision is made for outside
equipment, such as a weatherproof RCD socket on each outside wall.

However, you should protect all socket circuits. This isn't a requirement,
but common sense. It is also common sense to ensure that it is on a
different RCD to the outside sockets, as these are quite likely to trip in
wet weather.

Christian.