In terms of normal everyday usage, it is appropriate to add "for" when a sentence starts with the word "except". This makes the sentence flow better. Where "except" appears mid-sentence, the "for" can be dropped. To illustrate my point, here are 2 sentences with the same meaning, but with "except" in different positions: 1. Everyone in our department has already signed up for the training course, except Jack. 2. Except for Jack, everyone in our department has already signed up for the training course. See the difference?

Just say: "I'm sorry.", "I'm so sorry.", "I'm sorry if I've offended you.", "I apologize for offending you." or "I'm terribly sorry." And if you've really crossed a line you can add stuff like "Can you please forgive me?" or "I really didn't mean it that way!" Except: The race pretty much went as predicted - except that Michael Schumacher actually came in last. Except for: Take of all his clothes except for his underwear! But then again, in the first sentence you could say: The race pretty much went as predicted - except for the fact that Michael Schumacher actually came in last. Maybe someone else can shine his or her light on the situation. :P