After consulting the lovely ladies at The Sewing Forum, and spending an hour and a half scouring google and Flikr for photo's of other people in their Sencha blouses, I'm much happier with the fit of mine, especially after changing that sleeve. It looks like creasing is unavoidable with cut on sleeves, and this blouse is meant to be a bit baggy. So I'm happy with it, and won't mess with it anymore.
What do you think? Does it look ok? Dom says it does, but I'd appreciate your opinion too :)