I have UPC in my new gaff but I'm at the opposite end of the house to where the router is and the signal is a bit shit - youtube is glitchy. Is having a usb wireless receiver at the end of a 5m usb cable likely to make it a bit crapper than no cable? Are some wireless receivers better than others? There isn't enough space under the doors for a network cable...
The long USB cable could work, or you get get a wireless repeater / range extender, or you could try powerline networking? i wouldn't use it myself though. I ran some Cat6 cable through a wall to my PC so that'll do me until UPC eventually open the internet taps all the way and hit their 1.3Gb/sec limit.