Hi andy
There quite straight forward to fit, most of them plug in the cigerette socket, better ones you can hardwire in
basically you mount front and rear cameras and then run the wires around the screen, tuck it in the trim, down the dash then under the door step plastic trims to the rear cam the same, up the side of the seat, around the screen to rear cam
most have a rechargeable battery built in, so when you switch ignotion on cameras come on, when ignition goes off they just shutoff in there own time under there own battery
I added a link at the bottom, it same sort of money as the one your looking at, but has front collision warning built in, for when you get to close to the car in front, it has lane depature warning, for when you drifting out of lane on motorways and also has all speed camera warnings built in, these can be switch off as well
if you looking at that on have a look at this one as well http://www.ebay.co.uk/itm/THINKWARE-F750-Complete-Kit-Front-Rear-Car-Charger-Hard-Wire-32GB-64GB-/301799655597?hash=item4644a948ad:g:uHkAAOSwuAVWy0QZ
cheers
Joe