So I ran a "stumbler" all the way from Waterloo East to Grove Park. [about 8 miles]. In that time it [KisMAC 0.21a] found 511 wireless networks. (which surprises me as somehow it finds them even when the train is travelling at 60mph, sometimes observing packets for up to 8 seconds)
Anyway, the security conscious will be pleased to known that of these 511 networks, none are practical for establising an
ssh connection to a known host.