There are always some places that can be secured on the day, BUT nothing is guaranteed. Some people get in on the day as people telephone to say they can"t play. After that, there"s the chance to play as an alternate. But in Walsall only one alternate got in. In Manchester it was a few more I believe.
The reserve list on the day is done on a first-come, first-served basis. Here"s an example. Lee Mulligan (the defending Welsh Champion incidentally), went up to the Scottish event without a seat. He waited outside the casino from 9am, and all but guaranteed his place at the top of the reserve list. He got in - as did several others.
Depends how much you want to play!