I need to find a 12V ign feed and earthing point. I'm guessing that the easiest place will be behind the head unit. Any advice on how to remove it?

You can poke the plastic bits from cotton buds down the side to release it.

Think that a kenwood stereo key will work too.

kenwood release keys do work thats wot i used to remove mine with

used blunt hacksaw blades in both our octy and my fabia to remove radios.