I've just ordered my new car and have delayed the registration until the 1st September. I didn't want to order from factory as less leverage for haggling so found one in stock to the spec I wanted that has just come in on the last shipment.
Managed to get £2500 off plus free GAP insurance so wasn't too bad. Plus, my car has 3 seperate problems with an expected bill of >£1500 and MOT is due next week. So i went in with the view to buy now to fix the price for my car but then delayed the pick up 3 weeks to get new plates.
It all depends on what deals are going on all the options so you have to take each scenario as it comes. This ended up being the best way for me on this occasion but other times I bought used as it was best deal, or went ex demo model etc.
One thing I do note, is that living in the NE there is about 100x less options! lol