Well, well. It just goes to show that there is such a thing as bad publicity for Ryanair. Because of all the negative reaction to O'Leary's arrogance in TV interviews over the weekend, and the fact that the lid had been blown off their little sting of refusing to collect £5 at the airport while still being prepared to charge people for a whole new ticket, they have backtracked - after a fashion.
They have finally put something on their website. The pertinent bit is this:
"[I]n accordance with Article 4.2.2 of Ryanair's General Conditions of Carriage, all affected passengers will be advised via email of the additional tax amount that will be automatically charged to the credit card or debit card used to pay for their original booking. These credit/debit card transactions will take place over the next 2 weeks."
What this means is that passengers won't be denied boarding if they didn't pay the tax in advance or buy a anew ticket (Ryanair obviously realised how bad that would look). But you will have your credit or debit card charged automatically instead.
This means that if you have decided not to fly for whatever reason, including not wanting to pay the extra duty (for reasons of affordability or principle) that's tough. They will charge you anyway.
Jet2 is also charging people's cards automatically. They and Ryanair are the only two I know of so far.