Like veecee, I cannot claim to have analyzed the scene quite so thoroughly, but the 5 networks thing did annoy me a bit.
First of all because, as you said, obviously Sherlock and John have their own wifi set up in the flat, so why does it not show up?
And secondly, I strongly doubt that "foreigners" living in London as criminal agents name der wifi-connections in the native languages? Most people I know here in Austria actually use English names, or simply use codes that only make sense to them.
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"There is no such word as 'impossible' in my dictionary. In fact, everything between 'herring' and 'marmalade' seems to be missing." Dirk Gently
Finally, I have made it to Cipher Expert :-))))) (8.8.2012)