What kind of discount should I get from a dealer?

Hi all, We have ordered a new motorhome and lots of extras (Total £55.000 with extras) with a part exchange on our old motorhome. We did not get a discount but £1950 of free extras that we wanted and £2000 extra on the top end book price of our old motorhome. Can anyone tell us if this was a good deal or should we expect better?. What is percentage should you try and get from a dealer and what are your experiances?