Just a quick question to any electrical experts in here.

I want to put a plug socket in my loft, but i'm not sure where to take
it from, as there are no ring main power cables up there, only
lighting cables.
There is however, the enormous cable for my shower!, (10mm T&E I
think) which i'm sure could easily supply a single power socket. The
thing is, I can't seem to find a junction box to take this size cable
(well, not at B&Q, Wickes etc.), although I haven't tried a merchants
yet. Also, is this the right way to join to a cable this size, or
indeed, is this meant to be done at all (i've been told, not by an
expert mind, that you should never run anything else from a shower
cable, only the shower).
The shower is 9.5 kW, so the 10mm cable must have plenty left for a
power circuit, i'd have thought). I guess the alternative is to take a
spur from a socket in one of the bedrooms etc., but I don't want to
upset any decorating. I just want to locate a suitable source already
i the loft.

Perhaps i'm going about this all the wrong way, if so can antone
suggest anything else (from the available cables in th loft).

I'm aware of the changes to wiring regulations recently, but not sure
if this applies to what I want to do, if so then I'll get someone
qualified to do it.

Graham