@Anansis. Did you have enough money on the prepaid card? If not a secret (and forum rules allow) what kind of MC Prepaid you have?
There's definitely enough money on the card- I topped it up specifically to book the flights in question. It's an Escape Prepaid card which I purchased from Phones 4U in the UK. I've been in contact with them and there are no problems with the card.
A quick Google search suggests that some people experienced similar problems last summer. However, I've used the card recently and have never had any problems before. I would call the Ryanair helpline but this would end up costing me more than the admin fee!
I'm a cynic by nature. If this is a problem with Ryanair I doubt they will be in a hurry to fix it...
