Tim S wrote:

Yes it's OK, but you must apply one of these to the outside:

http://www.tlc-direct.co.uk/Products/TLLAB50.html

to warn anyone coming after you.

I've occasionally wondered what practical problem this is supposed to
prevent in a domestic setting. I understand that the colours for
three-phase have changed in an undesirable way (neutral / phase swap, is
it?) but there's no such confusion in a single-phase system. Black and
blue are both always neutral, red and brown are both always live.
Tradesmen and DIYers are going to be aware of the old colours for many
decades yet as they show up in existing installations. And even if some
new kid in 2080 doesn't know what this red conductor is that he's found,
I doubt the actual wording on that sticker would help anyway.

Still, for 30p I stuck one on - nice to make things look official :-)

Pete