Finding a cable within a wall?!

["noel_pilot" <HA@xxxxxxxxxxxxxxxxxx>]

Hi all,
Running a new cable from the loft - power but definitely for HA cos it
will eventually be to power the loftbox!!

I have the space between the walls ok, have pushed the cable a
suitable distance down and think it should be near the socket i have
in the bedroom below.

Only trouble is, when I remove the socket below I can't see/feel the
cable from the loft!

So....how do I find it?! There's insulation between the wall, I was
thinking about a pipe/cable detector but I believe that they will only
find mains connected cables which of coures this isn't yet!!

So...any ideas from the professionals?!

Thanks

Noel