Almost everywhere now you can get on BTFON, which is BT openzone , check your wifi networks right now and see! - if you're a mobile phone subscriber it's very likely you'll have a username and password to use their hotspots - for free. Just call your operator and ask for username and password.
And.. well if not... of course for educational purposes only - KisMac will quickly crack a wep key.... not that I ever use that.
I agree that your most cost effective route is to go begging from your new neighbours - I'm sure you'll pick up 2 or 3 signals there. Plus it's a good ice breaker to be asking favours so early on!! ha.
As mentioned, BTFON is available as lots of BT Home Hubs around (It's even available at my house as we speak) and some mobiles (O2 Iphone for example) include free access to BT Openzone so you could use your mobile over the BT WiFi.
Quick update - sent in the Objective Eye diplomatic core (aka my girlfriend...) to speak to Virgin again. The long and the short of it is virgin will be disconnecting the old house on Wednesday and connecting the new house on Thursday. Reducing the down time from 10 days to about 10 hours.