Just had a quick skeet & depending on the resolution offered (maybe you will be able to reduce it?) it looks like medium quality is around 700mb per hour, high res (1080p) around 2 - 3gb per hour, I could be way out, but it's the best I can find at the moment.
(just seen all or most, of their youtube vids are 480p, so if the broadcast is the same then you may be looking at 700mb)