Just got myself one of these
https://www.currys.co.uk/gbuk/cameras-a ... 6-pdt.htmland it's brilliant !
Goes over your rear view mirror and records inside and outside the vehicle at the same time. The picture quality is excellent, even at night in dark areas everything can clearly be seen. It picks up moving reg. plates at night (might need to use video software to change contrast/brightness to see them). Theres a seperate mini camera - says it's for putting on the rear of the car as a parking camera - but can be put anywhere inside. I've put mine just to the side of the rear view mirror and you can see ALL of the interior, front and rear. The picture is dark on the interior with lights off, but you can clearly see the rear passengers with the interior light on or as you go past streetlamps.
It's got a few gimmicky features you'll never use but if you're after a cheap dashcam this is'nt bad for £40 + a microsd card.