I bought an antenna (from Maplin) that effectively takes the aerial out from behind the PC to the top of the case - this has a DRAMATIC effect on reception!
To further improve the signal, I made a parabolic reflector from the cardboard tube a bottle of whisky came in (single malt, natch) cut in half then down the middle (but retaining the metal base) then covered in tinfoil!
Works a treat, not just in improving the reception of my own signal, but helps by blocking out neighbouring signals from the "wrong" directions!
Not elegant, but what the hell!
SD