A few years ago I bought some Homeplug devices for distributing the network around the house. For me, this was the ideal solution. It utilised the existing electrical network (instead of installing ethernet), and provided a WiFi access point in the remote room (and an ethernet port). If I wanted the network in a different room, all I had to do was unplug in one room, and plug-in in the other. Simples!

However, it seems they aren't available for sale any longer. I can't imagine why.