Just to pick up on this topic there are a couple of things to add/clarify.
As I understand it (from a local police officer)
car camera LCD screens can not legally be viewed by the driver!
so most suction cup mounted car cams with LCD screens are illegal, by token of the fact most, if not all provide an LCD TV screen which CAN remain on, or on which the default is on.
Apparently there is also a clear guideline for mounting any 'object' on the front windscreen and this is as follows -
The specific act of placing stickers in car windows is not in itself illegal. However, it is an offence, under
regulation 30 of The Road Vehicles (Construction & Use)Regulations 1986 (SI 1986 No. 1078),
to drive a vehicle in which the glass is maintained in such a condition that the vision of
the driver is impaired.
If you use a screen mounted car camera in the UK, if the device (camera and / or cradle and / or suction cup) intrudes more than 4cm into the secondary (pink) wiper clearance zone, or intrudes more than 1cm into the primary (red) wiper clearance zone of the windscreen, you are committing a serious traffic offence (dangerous driving) under the UK Road Traffic Act 1988, and your vehicle is not roadworthy (it would fail an MOT).
There are a lot of cars in the UK where the windscreen wipes so much of the screen that it is impossible to fit a dashcam outside of the limits mentioned - and even if they can be fitted, because the wipers will not clean the screen in front of the camera it makes them almost useless in rain or when the screen gets dusty/dirty.
The other interesting point concerns retailers of dashcams.
UK sellers of these devices must disclose which vehicles their units can be lawfully used in. Legal use means the suction cup, cradle and camera must NOT intrude more than the 1cm/4cm limit into the wiper clearance zone of a vehicle, and any active LCD screen must NOT be visible to the driver. As the wiper clearance zone varies from vehicle to vehicle, the seller must physically test their car cameras to make sure it is possible, or to obtain specification on the wiper clearance zone from the vehicle manufacturer to be able to determine this. If they can not / do not disclose whether their units can be legally used in your particular vehicle's make and model, they are breaking the law by causing you to commit a motoring offense of dangerous driving. In addition, the seller of the car camera MUST explicitly make you aware of the fact the camera (suction cup, cradle and camera) must NOT intrude more than the 1cm/4cm limit into the wiper clearance zone of your vehicle, or again they are causing you to commit a traffic offence.
Now I have not seen one UK (or international site selling to the UK) that mentions the above.
So - pays your money, takes your choice (or risk as the case may be).