In reply to Kimono:
you've got 3 basic options.
1+get broadband in the house.
2+use a mobile/dongle (basically the same)
3+use broadband outside the house
1/ your neighbours don't have it, you have no phone line. You're stuck.
What I'd suggest is get the phone line put in, except the £15 ish a month for the 6 months you're not there (assuming you can't find a short term contract for it but I've done one google search below for you, you can do that bit). Then look at these short term contracts for broadband -
http://www.uswitch.com/broadband/compare/short_contract_broadband/
2/ someone said above 3mobile now have a 2G tether limit. That may be more up to date than my experience, but I was broadbandless about a year ago ish and then again about 8 months ago ish. the first time I went nearly 6 weeks tethering, the second was I thnk about 2-3 weeks using my 3mobile phone. Surprisingly fast at 2mb/second, I was streaming films on netflix, music on spotify, spending a lot of time browsing (I was in the middle of researching for going self employed so was doing a LOT online) and even managed a little bit of gaming during that time at decent speed!
May have helped that I was using an app called PDANET+ (paid the £6 for the premium version which was worth it) so it might have got aroudn the normal limits. Also helps IMMENSELY with config issues between different phones and network card issues. I still use it now at times.
3/ what do you need the net for? If it's just now and then a lot of bars and cafes now have wifi. I sometimes work out of the local wetherspoons for a change of scenery. Their wifi goes a bit crap in the evening for some reason but during the day it's pretty good. Free refills on your filter coffee until 9-2pm too!