For future reference, you might want to look into giffgaff. They have free sim cards and very aggressive prepaid plans. I get the impression they are still kind of new and wanting to build up a customer base.

The only thing I'm not sure about is whether you can pick up a sim card in person at a local shop. They mail you one for free, but you need an address to mail to. I had mine mailed to a friend's house, but you might be able to mail one to your name at a hotel's address....