[matthewcornish]

I think unless you're going to go from the 118D to something at the other end of the scale then it's probably best waiting until you can afford something better. I almost did the same as you last year, going from my 116D M Sport to a 118i M Sport but am very glad I backed out of the idea. You never know how your situation will change. For me a year on I'm now fortunate enough to be two weeks away from picking up my M135i (bit more of an upgrade).