This decision makes the one I made last year about proposing to my now fiancee look like a mere whim.
I heard just over a year ago that a higher powere diesel Fiesta was in the pipeline. I know nothing more than that but would expect it to have the 100ps engine in it. I owned the current TDCi which has the 1.4 75ps engine and thought for what it was it went really well (except I found is sadly lacking in 2nd and 3rd gear accelleration). It did return however an easy 40mpg even with me giving it full beans almost everwhere.
Now, if a 100ps, or even 115ps diesel Fiesta was produced, I would have a serious dilemma over whether to get that or the ST.