thanks so much for the replies it really helps!
I totally get the fish in the goldfish bowl analogy (much better than my conveyor belt analogy): The wind velocity is irrelevant once in the air, or only relevant to your ground velocity.
I just don't understand then how a headwind can contribute to TAS on take off (air flow over the wings as stated above) and then be irrelevant to airflow over the wings when airborne.
To me this seems like the headwind being the water in the goldfish bowl during take off and then becoming the goldfish bowl once in the air!