Stuart check Midland, it is cheap, and it has good reviews and it has a housing rated for 85m, it is not as expensive as the GoPro, and made perfect to be installed on one side of your dive helmet, I'm considering this camera my self.
XTC400 - Action cam Full HD with WI-FI - C1106.01 - Midland Europe
CC-XTC400 MOUNT - CUSTODIA / XTC400 - C1121 - Midland Europe
XTC400 - Action cam Full HD with WI-FI - C1106.01 - Midland Europe
CC-XTC400 MOUNT - CUSTODIA / XTC400 - C1121 - Midland Europe