Have you thought about buying a cheap HD Flip camera? I see them going for 75 quid on Amazon UK.
I use a Flip Mino HD mounted to the car using a suction cup mount (Fat Gecko Mount by Delkin)
Does a lovely job - and can be charged using a standard USB charge lead from the car.
Here are some samples:
Mounted to the exterior glass - 911 going up Hwy 89 to Yarnell in AZ (Select the 720p version in YouTube)
[video=youtube;m6T8sUsE64Y]http://www.youtube.com/watch?v=m6T8sUsE64Y&hd=1[/video]
http://www.youtube.com/watch?v=m6T8sUsE64Y&hd=1
Mounted inside the windshield of my Discovery II - off-road near Sedona AZ heading out to Devils Bridge. (Select the 720p version in YouTube)
[video=youtube;OiegZi93uPE]http://www.youtube.com/watch?v=OiegZi93uPE&hd=1[/video]
http://www.youtube.com/watch?v=OiegZi93uPE&hd=1
Great little HD camera, with lovely image quality, and light weight/small size.
The road to Yarnell is just an amazing drive - lots of twists as you climb the hill from the desert into the mountains.
[MAPS]http://maps.google.com/maps?hl=en&safe=off&q=Yarnell+az&gs_sm=e&gs_upl=1155l1915l0l2236l4l3l0l0l0l0l279l606l0.2.1l3l0&bav=on.2,or.r_gc.r_pw.&biw=1869&bih=1086&um=1&ie=UTF-8&sa=N&tab=wl[/MAPS]
Zoom in and take a look at the road south of the town - this is the stretch in the first video