Transcend Drive Pro 200 is a decent Dash Cam under £100 IMO, Had mine since June hardwired into the sunroof power feed, no problems here, Surprisingly good quality video/sound for a £79 cam...
Also has WiFi with a iPhone / Android app with many features, Set cams date/time over WiFi from the phones current time/date, Can mirror what's seen on the camera on your phone and if needed wirelessly transfer video clips to your phones camera roll, Adjust camera setting on phone etc...
Set this on HD and you can see how clear the registration plates are
LinkAlso good at night
LinkThe max size memory card you can put is a 32GB micro SD card which will roughly capture 3-4 hours of video on 1080p setting can be adjusted to 720p although I've not tried this so couldn't say what that's like. You can also set on loop record if you wanted.
Also has a G-Sensor which sometimes activates the camera to record a protected file under hard acceleration / braking. The sensitivity can be adjusted mind.