Where is the easiest place to ground my headunit?
Its all plastic behind it, except next to the glove box, where there is some sort of metallic thingy

Thanks

You don't need to its part of the wiring loom.

Sent from my Nexus 4 using Tapatalk

Its to bypass some sort of parking break security mechanism, you could ground the wire instead.

I don't understand your last post, but there will be an earth behind the trim below the steering wheel somewhere.

Sent from my Nexus 4 using Tapatalk

Have you got a double din unit with DVD player and talking about the handbrake cable which stops/allows a picture when driving?

Ground it with the earth wire coming to the head unit

I attached mine to the hazard switch so that it thinks the handbrakes on. Saying that ive only had a DVD in it once to check it in the year of having my double din headunit.