I'm with Pups here.
OK, you're 31 and you do have a chance to make the money back.
I wouldn't go with Oxford's APP programme only because I don't think it gives you any thing more than a good modular course would.
Whatever you do, don't get suckered into believing the glossy brochures of any school without applying the same questions you would to buying a house. You can sell a house, you can't sell a log book.... (unless you're a 737 TRE...)
What you MUST realise is that unless you move very quickly time is possibly against you. Now you are going to spend the cash that would have set you up for retirement.
If I were you, I would go modular (but do it full time) IF you can afford it without going into debt.
If you are going into significant debt, rethink your strategy.
I don't want your money, I don't need your business, I am not posting to feather your dream. I just don't want to see you 55 or 60 with **** all to fund your pension.
Put your emotions aside and think as an accountant would. You have to. No one else will.
Good luck.