Ryanair online check-in problem

I booked a flight from Belfast to Birstol from June 8th - 11th. I booked it on May 17th before all the new regulations came in on May 20th. I opted for online check-in as it was the cheapest but when I went to print out my boarding card I found out that they didn't accept driving licences (I don't have a passport).

It turns out that they only accept driving licences for airport check-ins that were booked before May 20th. I was wondering if there was any way to change my booking to airport check-in instead and so that the pre-May 20th rules still apply. If I didn't check-in online and just showed up at the airport and went to the airport check-in would I be able to use my driving licence then (despite a fine)?

I would really appreciate any help anybody can give me on this problem.

Thanks, Lucy