However, once airborne, I shall disrobe in the toilets, and return to my seat.
When the cabin crew, under the captains authority, ask you to put your clothes back on, which they will, what are you going to do then? I will tell you that ignoring or not following lawful commands of the crew and captain is illegal and dangerous and you will be in contravention of the Air Navigation Order.
This is about demonstrating that naturists the world over have nothing to fear from practising their favoured activity in a much wider variety of situations.
Except that you are demonstrating your fear by remaining clothed during the check in process. You're compromising your philosophy old son.
Do you really think that you will be somehow 'protected' once you are airborne?
Be prepared to either return to your point of departure and be met by the police or be prepared to arrive at your destination and be met by the police.