Silent Witness SW010. I have these in both my cars for years front and rear (hard wired), fit and forget. They are a UK company and you pay a little more...failing that, buy them direct from China, they are cheaper, but you will have to pay import charges and take your chances!!
If you are unfortunate to need to use footage and supply to the police, you can upload it to them and they will see that it gets to the correct police authority.
http://www.silentwitness.co.uk/dash-cameras/SW010, Silent Witness