Ah, what you need is a Wi-Spy!
http://www.wi-spy.co.uk/
http://cpc.farnell.com/unbranded/72-...ser/dp/IN05456
Every wi-fi card I've used has some sort of configuration utility that lets you look at what channels are available. Here's a screen grab from one I use:
Crowded round here init! I've actually seen one more than that too. So there's no way I'd just fit and forget.