The aerial in the loft suggests that it connects to something.
It's unlikely that your aerial won't be compatible with Freeview but it could be:
1. Your socket isn't connected to the aerial.
2. Your aerial needs adjusting to pick up the signal
3. There could be a problem with wiring (ie. Broken wires)
Have you checked to see if you can tell where the wires run from the aerial and where to?
Are there any other sockets you could test it on?
If not, try moving the aerial around.
Another idea but may be a little messy......run a piece of aerial wire from the aerial down through the loft hatch (lose loose so you can test it), put an aerial plug on the end, plug it into the TV (which by this time will be upstairs!) And then try tuning it. If it doesn't work, adjust the aerial. If/when you get it sorted, plug the TV back in downstairs and test it. If it doesn't work, you know the socket isn't connected. Messy but it's an idea ;-)