I really would not recommend using the wires int he roof console. These may have multiplexed wiring connections to other systems that will not tolerate other non CAN equipment attached and any splicing can affect the data communication.
It really is recommended to wire directly to a fusebox using a piggy back connector that protects both the accessory, but more importantly the vehicle's systems.
Some of the passenger fuseboxes are wired onto and around the BSI which is the brain or master computer on the vehicle, so caution is advised not to disturb any connections here as room can be a bit tight.
The dashcam should ideally be mounted in a legal position that isn't going to obstruct your view (generally top centre or just off centre), where the wiring can be routed along the top windscreen headlining, down through the A Pillar. If you are going to route the wiring inside the A Pillar, make sure you fasten ay wires BEHIND any existing wiring there which is likely to be the side / curtain Airbags, as you don't want any wires in front of this in case of deployment as it will act like high-speed cheesewire!
You should then be able to route it down and out of the A Pillar and then into the end of the dashboard, where the ends have a trim panel that can be removed, which will give you access to the inside near where the BSI is located and should facilitate a better access to the fuse box and a suitable earthing point on the vehicle body.
Here's the end panel of the dash:
Just use trim removal tools to remove this, but be careful as this contains the passenger airbag deactivation switch shown below. Just work your way around and then disconnect the electrical connection from the inside to remove the panel.:
That should give you better access to the fuses.
You then need to determine whether you want a permanent live or a switched live. Personally I only use a switched live, so the dash cam comes on and goes off automatically with the car ignition, which saves me having to manually turn it on and off, and secondly, prevents forgetting to turn it off and discharging the battery.
Even though some dash cams are supposed to have a low voltage detection and turn themselves off, they may not be reliable.
Although different vehicles, I've fitted one in my C3 Aircross
here:
... and in my C5
Here
... using similar techniques. The images may give you some idea concerning the end of dash access I'm talking about above.