Picked up a BlackVue 380G last week for £100 as they were being sold off due to the incoming model.

Really pleased with the ease of installation with no visible wiring.

For anyone else doing this:

1) Remove glovebox for ease of access to fuses.
2) Gently prise off "Airbag" cover on side airbag on A pillar.
3) Unscrew (Torx) screw holding cover in place. Pull off door seal and remove trim
4) Undo screw holding side speaker panel in place and remove.
5) Mount Blackvue below and behind rear view mirror.
6) Starting behind the glovebox, route the power cable out the side front, up along the wiring in the A pillar, tick under the headlong until it reaches the mirror.
7) Connect a 12V socket across a piggyback fuse holder in fuse F5, and a ground to a convenient bolt.
Plug it in and put everything back. 2011 MY SD4 HSE + planning some interesting stuff
Previously: 2004 Discovery Td5 ES Premium + lots of stuff
Previously: P38A Range Rover 4.0 SE
Hampshire and Berkshire 4x4 Response Founder and Treasurer

Where did you get it from for £100?

Step 3 - do you mean the air bag cover? I thought in step 2 this came off by prising? * GONE. GS TD4 Manual MY2013. Orkney Grey with privacy, cold and clearview packs, armrests (a must!) and a spoiler.
* 2011 4.4 TDV8 Full Fat. Amazing piece of kit.
* GONE.2012 RR Sport HSE SDV6 Orkney Grey. Rocket ship. 33mpg.
* Range Rover Classic '93 200Tdi Factory fit
* 1949 80" in family since 1975

A-pillar have a plastic cover saying airbag, behind that is the torx screw

With the exception of (4) thats exactly how I did mine. Mine is usually parked up at home under a cover during the week so I needed a way to power down camera (I didn't want to have to keep pulling the power cord out of it) so I also connected it up to a Power Magic Pro under the drivers side dash, the pro version has a switch on it, in the 'On' position it allows the camera to stay awake when the car goes to sleep ( the default park mode), when in the 'Off' position the camera will power down when the car goes to sleep.

So I do have to remember to set the switch to on when I leave home otherwise I'll only get park mode until the car goes to sleep, and I also have to remember to set the switch off when I park up at home otherwise it will run in park mode until it hits the low battery switch off point. 
Hung like Einstein, smart as a horse.

Running on a Power Magic, no issues with the battery, fit and forget.
Yes Torx Screw behind the airbag panel