Thank you for the replies.
I got to thinking that instead of having a gopro on your bike helmet, maybe something lighter like a webcam, connected to the smartphone for power and data transfer…that way you can use the smartphones screen to ensure the shots are framed properly (and not pointing directly at the front wheel!!!) as well as lightening up your bike helmet.
A quick look on youtube suggests that Android devices can power such external devices as well as transfer the data through their ‘ on the go’ technology. Sadly, Apple products of recent years don’t supply enough power via the camera connection kit.
I,m not totally sold on any of the android devices and still have my eyes on the Nokia 820 ‘cos of the free navigation apps.
Anyway, I had quick look around DealXtreme and I stumbled upon this,
http://dx.com/p/sj212-waterproof-cmos-12-0-mp-wide-angle-1080p-hd-sports-camera-w-hdmi-tf-usb-av-out-black-239203
Its got the autofocus, image stabilisation and a load of mounts as well as being cheap so maybe its got the nod!