Any question answered...

It's a new build so we assumed the developer had installed an aerial. We can't see one on the roof but thought maybe it was in the loft/roof.

I suppose they could have just installed the cables but not hooked them up. Just wanted to check I wasn't missing anything obvious

I had had the same. New build, dead sockets.
It turned out the were connected to an aerial in the loft, right next to the water tank, which frankly does fuck all.

Same for the phone sockets - not connected to anything (£125 for a BT technician per socket to make it work).