Gibbo - if you are taken on by someone, please be aware that they will not be paying your national insurance and state pension contributions - which sounds irrelevant when you are 14. But that means that your employer is getting you much cheaper than anyone over 16, and when you are 60 the days / weeks / months of graft you put in aren't paying you any pension.
In one school where I taught, a Y10 girl used to come in weary cos she'd been serving at a chippy till 1.00 am - the owners were her best mates till she was 16 then they 'didn't need her any more'. She chucked away her chance of doing GCSE's first time round, for a couple of quid a week.
Now if it is the case that you desperately need money to survive, find someone like a school-based youth or social worker to talk to - even your head of year at school should be able to put you in touch with somone who will help. If this is not a survival issue, can I suggest you weed your neighbours gardens for a fiver?