In September 2013, I ordered a GoPro Hero 3 Silver from http://www.tartybikes.co.uk (affiliated with a member on WSCC). I opted for a roll bar mount to go with it.
It came with a reasonable amount of accessories. There are two enclosures, one fully sealed and one with an open back. It says to use the fully sealed ones when likely to go above 100mph. To be honest, I find the sound quite muffled from the two trackdays I’ve used it on. I think I’ll try the one iwht the open back next, assuming it is dry of course. If that captures too much wind noise, I’ll get an external microphone.