Your post is unclear.
Are you saying you need a perm live and neutral supply for a fan and light you have started to wire?
If you take the supply from the light switch you mention, it must have a neutral. Switches often don't have a neutral, even if there are black or blue wires present.
To wire from a socket circuit you would need to do this via a fused spur unit, with a 3 amp fuse in it. More details of the socket circuit are needed first before connecting up.
EDIT. When I replied to this it seemed there were no replies. May be going mad, or site playing up.
I tried take from the switch wasn't any neutral there only live, so it is out. now I am going to get (L) (N) (E) from a socket via a fused spur unit, with a 3 amp fuse in it