Leave it parked and unattended near Gavs for 20 minutes, and when you return it'll have been removed, along with the wheels and anything else that's shiny!
You need the special tools to remoove that model of head unit. They are easy enough to get hold of but they are not cheap. About £20 ish. But if you can take it to halfords and they will whip it out for you for a small fee.