Honestly?! 
I assume you mean a main dealer as well & not a broker................If so which dealer?
Yeah i did it by phone though rather than going into the dealer as i live in the middle of nowhere. nearest dealer 50 miles away and wasn't going to do any discounts so called glasgow and said what deals were going on the net and asked the best price they could do. They came back with a price over 1k less than RRP, bit of haggling, another call or 2, said if he lowered it to xxx then i would give him my switch card details and buy it. Called back 2 mins later and agreed to the price i asked for. Admitadly i have alot of options on the car so maybe it gave them a bit more scope to work on.
I think as Kev mentioned ealer, dont seem too keen, if you do that they know you want it and will pay full wack. Say you were hoping for a figure of xxx (maybe 1500 or 2 k less) and then keep negotiatingand meet somewhere inbetween. If they are not interested, they may call you back. You could even say on leaving, lower the price to xxx and call me and i will buy it.
Might work, might not, the least i have ever got off a new golf is £1500.