You're right, thinking and knowing are two seperate things, and
without contacting the builder I can't be sure.

However, the reason I thought there was power there is because I found
what I suspected was the other end of the wire in the loft not plugged
into the distribution amp. If it's not plugged into anything that end
then I don't see how any static or anything could get down the wire,
so could that mean that power is provided onto it somewhere else down
the line?

Thanks again for all your help, though I suspect I may have to pose
the question to the builders to find out what's connected to what!