OK guys, thanks.
A hard wired connection would be possible but it would involve a little architectural work if I wanted to avoid running wires down the hall. The modem/hub is in the hall and my PC is in the living room. In between is the kitchen and all the metallic bits in there wrecked the wireless signal which is why I went Powerline in the 1st place.
I also have various media devices powerlined on the network; Humax digibox, amp & dvd player (not to mention 2 phones and an iPad on wifi). Would these leach bandwidth even if they weren't in use at the time of any test? I also tested speed through my iPad (wifi) and only got about 10.
Finally, I got some really weird results from BT Speedtester; e.g. ~ 2 when other sites were showing high twenties.