Yes, the waiting is over, the tickets are available!
Just follow these easy steps:
1.) Register with the Games Expo.
2.) Confirm the e-mail they send you.
3.) Sign in.
4.) Go to the Tickets -> Entrance Tickets drop down menu.
5.) Choose whichever ticket applies to you. The UK Masters is a 2 day event on the Saturday and Sunday, so I'd pick Weekend Adult personally.
6.) Go to the Events -> Miniatures drop down menu.
7.) Select War-Machines Hordes UK Masters tickets.
8.) Pay for it all.
9.) You're done.
Tickets are selling VERY quickly (at the time of this writing there are 47 left - after being on sale for 3 hours) so get into gear and get those tickets!
Information and the rules pack is available on the Privateer Press forums here.