Thanks all. I should have said that the buyer is someone I know who would understand if I changed my mind as he's getting a very, very good deal and he knows it. There would be no issues there, believe me.
To your point, Carbon Unit, you can undoubtably buy better when buying a complete bike but I frankly, I can't afford to update my whole bike and keep the same quality gruppo/wheels in one go. Neverthless, new kit with warranty is no small thing.

Overall, my intuition is to stick with the plan and it seems you guys are confirming that.