Well, it took a little longer than expected, and a call to the customer support line, but I am now wireless enabled. To my surprise, the customer support line tech was not only very courteous, but straight to the point and devastatingly helpful. Even though I called at around 9.30 in the evening, he sorted out my one remaining problem in about 5 minutes flat. For the tech heads who are interested in what the problem was - the documentation told you how to change the DNS servers on the Internet Protocol connection settings to allow your PC to talk to the router, in order to let you set it up, but what it didn't tell you was that after you set everything up, you then had to check the system log to get the DNS addresses that would allow you to connect to the internet. So, just a dodgy step in the documentation, more than anything else, and very easily solveable once you swallow your pride and call technical support.
Fleur, apparently, does not block radio signals, much to my relief. She did, however, insist that the router and USB dongle were hidden as out of sight as possible. We don't want to ruin the aesthetics of the flat, after all, do we?
So, my job tonight is to enable the network security on my new wireless network, which will probably take me all night again (hopefully not), and then I can try hooking up the Xbox to the Ethernet switch, and see what happens. Once that's all done, I'm going to install the USB dongle drivers on my laptop, so I can link that in wirelessly, too. Or, if I can find one cheap enough, I might just get a wireless PC card... this technology stuff gets compulsive after a while. Must! Have! Gadgets!