If you have decided that you must have the car then go back to the dealer and say you'll sign straight away if the'll take £500.00 off if still no go ask for other accessories chucked in. It has worked for me every time I've gone to get a new car.
If the dealer offered you £380 off already without much prompting then their is more to go. Start at 600 and compromise at 500 off. Chances are they have other cars on order that can easily replace the showroom car.