Where to buy a bike?

I really want to buy a cheap, used bike when I come over (ONE WEEK!!), but I don't really know where to look.  Classifieds?  Flyers in the corner shop?  Shops?  No idea.  Preferably, I'd like to find something local, so I didn't have to worry about putting it on the train/bus.  I have a feeling a bike shop would be more expensive than I'd want...any ideas?

There are lots of bike shops in my area.  I'm sure you won't have too much difficulty finding one where you will be. 

I got mine off of ebay- just do a local search. It will be really cheap if you're outside London.

My husband got his from our borough's bike club and it only cost £10.  He was thrilled.  I think he called the council and asked if there were any bike organisations and they gave him the contact info of the people who run the group. 

How about Loot, Gumtree and Craigslist?

Police auctions are great places to pick up unclaimed bikes. For £50 you can win a bike worth £200 with all the trimmings e.g gripshift gears, disc brakes, suspension, etc.

Thanks, guys!  I'll let you know how it goes.

You may want to check with your Student Union.  IIRC, you're coming over as a student?  Here in Manchester, as far as I know, you can rent or buy (used) bikes through somebody there.  The guy even maintains it for you.