It's an international one, not just UK and you don't do direct swaps, you put up your list and when you give a book to someone you get points to use to get books you want. In some ways it's a lot easier but it's bit slower, people don't seem to rush to post out. I've had about 8 books from it in a month so far I think, all gone well.
You get more points for doing international post and most people use surface mail to keep costs down.
Just if you use both remember to knock any books you send out off the other list!