Pay to use the toilet...

Almost everyone I know have, at some point, flown with RyanAir (or other lowfare airlines). I actually flew with them withing their first year of establishment here in Stockholm. I think it was back in 1997. Not much has changed since then. They were cheap then, and they're still cheap today. Basically the only thing your paying for when you buy the ticket is a chair on the flight. Everything else costs extra: luggage, snacks, drinks and now you might even have to start paying for using the toilet onboard.

I think it's a good idea. Have you seen the condition the toilets on the flight normally are in? They're NASTY! Especially if you're flying with a lowfare airline.
My theory is that the people who trash the toilets are amongst those who wouldn't want to pay £1 to use it. Maybe this way, the toilet's will stay somewhat clean and the rest of us civilized people actually can use it.