Well when you are looking at £14,000 E class you are getting the 7g+ box now I have driven the 7g and the 7g+ and the 7g+ is a better box it has a different ATF oil ,i am hoping to get my hands on a 9g car to see what that new box is like the price of those cars will have to come down a fair bit before I can buy one of them,with the cars you are thinking of buying the 2.1 will give you great mpg,even the 2.5 returns good mpg,when you get to the 350 then you are starting to sacrifice mpg ,it sounds like you have no trade in so I would expect you can drive a decent deal.