Little Help Here ?

I'm trying to fit a new head unit to my '00 HGT Punto.
I've fitted the facia adaptor (after MUCH cutting and shutting - thanks to Halfords for selling me 'The Right Part' which was never going to fit) but the problem i have now is when i try to push the head unit into the dash slot. It goes almost all the way in but stops with about an inch to go as there are so many wires behind it.
So can anyone tell me how to get the slot/air vent assembly out of the dash so that i can route the cables without them getting in the way of the head unit when it's slotted in?
Or anything else i can remove to get a hand in behind the dash?
Any info gratefully received!!!!!!!

If you play around with the wires there are gaps that they fit into so you will be able tuck them around so the HU will go in eventually.

Thanks mate, i'll give it a try.