Forgive me for mentioning the wrong card daz, does not detract from my point. I admire your devotion to Ryaiar it counters the many negatives from others.
I do travel a lot on average 50-60 flights a year (including some on Ryaiair and maybe more now they are returning to Manchester)
So I repeat I see no point in getting a prepaid Mastercard just for flights with Ryanair, I simply factor in the CC costs, which you get on all airlines into the decision on who to book with.