You could start off on Amazon's kindle store - it's free, and has a reasonable footprint. Maybe find someone who's old enough to sign up to that (even though you could probably cheat) - there's no financial risk so easier to convince someone, and then see if they'd sign up for a google developer account for you. I think that the Google Play store is a cess pit of bad apps and preferential marketing, if nobody knows about your app then there's no point in even releasing it... there is a more positive outlook on the Apple store at least, but I think that should be funded by app earnings, £100 is a chunk of money to risk. I think that ideally you'd find someone old enough who knows a bit about marketing, and might be able to help you promote your apps and look after the bank stuff.
The code is dark and full of errors