My view in these cases is that yes, you should push the dealer you bought it from to sort it out. They are obligated to sort it under the trades description act or in extreme cases you could reject the car. In this case though they do seem to be playing ball and probably just need a little poke to handle things so it's not worth getting all hot under the collar about it really.
There's a wealth of information on this on the SPTL section of Pistonheads (Just have a browse around to see other's experiences in similar situations).
https://www.pistonheads.com/gassing/forum.asp?h=0&f=10
Michael.