I've just got Roadhawk Ride. Very impressed with it so far, smaller than I thought it would be and comes with a multitude of different mounts. Records in a loop so all you have to do is switch it on at the start and switch it off at the end. If you put in a big memory card I think it records about 8 hours before overwriting the oldest files. Battery life might not be what you're looking for at around 90 minutes but it comes with cables to attach to an external battery.
Halfords was the cheapest I could find and work do a 20% voucher scheme which meant I got it for just under £100