If you do get your PhD just don't put it on your OXford/Jerez application form thus avoiding the situation of them sneering at you for being overqualified. I don't think they really care in your employment history so the three year hole in your CV will be fine.
Obviously when you apply to British Airways mention it but Ryanair don't need to know.
I have seen all sorts of people training for ATPL eg medical doctors, dentists, pharmacists, lawyers, accountants, lorry drivers etc.
I don't think jerez/oxford will give a to$$ as long as you have above the minimum required and pass the aptitude test.