Monkeytoo - Taking my point rearding the purchase of extra seats a bit further - yes this does happen for the reasons I mentioned before, but I think in the case of the airline I fly for, the tour rep would have sorted out all formalities and obtained a medical certificate where appropriate so that everything was in order when the pax came to check in. Not the case I assume in this instance, so not totally the fault of Ryanair, but I still feel their customer service from all areas appears severely lacking.
On the issue of cabin secure.....where is your part of the world?? I have landed only once in 20 years with the cabin not being secure dues to a pax not in his seat. he was arrested upon landing, but thats another story. So I am surprised when you appear to say that it is a regular occurance to land without the cabin being secure.