Call them and ask - they might surprise, especially if the baggage is paid for on the same booking. I recently had to change the spelling of a name on a booking. I was resigned to paying a fortune, but Ryanair did it for free and it only took about two minutes.
There's a local rate phone number on the website. The phone call will cost buttons so its definitely worth checking with them. Good luck, and please let me know how you get on for future reference
