Thanks. As it happens, this is a new build extension. When I remove the
switch, there is in fact a blue wire in there, but not concected to
anything. Can I assume this is neutral? Does this therefore open up
the possibilities of what I can use?

You can never assume anything with electrical installations. However, you
can be optimistic. You'll need to test that wire to see if it is indeed a
suitable neutral.

Christian.