Skip raileurope.com if you’re in the US and buying rain tickets for travel within the UK. Their prices are outrageously marked up. For a Saturday, second class ticket from Newcastle to Edinburgh in October, their quote is $96.00. Get a quote from one of the many web sites based in the UK, and its 9 and a half Pounds. That’s about $17.
The problem is many sites in the UK don’t let you purchase tickets with a non-UK billing address. If you’re going to be at a major station where you can pick up tickets from a machine, check out thetrainline.com. They’re cool with US billing addresses, and much cheaper as well.