If you believe that you be self-employed and reclaim VAT and income tax (UK ), then why not employ an accountant and give it go?
But in my experience, you won't get far. It took me four years to train and to explain the ins and out of self-employment and the badges of trade would mean I would be writing a thesis. You could visit an accountant's office, pay for advice pertinent to your own situation and plans and see what they say.
I cannot advise on Ryanair as I have never seen or read their employment contracts. But presumably if you have one of their freelance contracts, you are free to work for other people as well?
Cheers
Whirls