Solution

158673

First name
Joe
School
Walton
Country
Age
12

I would pick the bottom amount because once you get to about £5 which would be about ten days in you'd double it meaning you'd have £10 which doubled again would =£20 and so on and so forth so I believe after 31 days not only would it be up to about £1,000 you would than have to add everything from all the past days on aswell so you'd be up to about 2,000