First 500 places were at $1 a pop. Sadly though I was ready at 4pm GMT I was in Taunton today and relying on my Windows Phone. The connection was poor and the rendering of the registration site surprisingly bad ( losing a quarter of the screen WTF!). After 40 mins of messing I managed to bag a ticket (needless to say that the $1 tickets went to the people with fast broadband).
Looks like MS is turning BUILD into a circus.