Is it illegal to run a mini business without a permit?

[Sam]

i am 14, i think its time i start making my own pocket money, at the moment, i am working with polymer clay and make pendants out of them. so far i sold 4 to my friends, then it cme to me, what if i start up a mini business where i could sell pendants to a bigger audience, i only mean set up a facebook page and possibly a youtube acount. would it be ok if i did this, i mean is it illegal, do i need to pay VAT or something, i live in UK btw. i dont wanna be arrested or anything,so if you say no, then i most likely wont do it. if it is possible to do it without a permit, do i still need to pay VAT or something? polymer clay is my favourite medium so i work really well, is it possible to start a business at such a young age. oh and i usually discuss what my friend want in school and exchange the pendant and money out of school (it is forbidden in our school to handle money and sell) if i can start a mini business, is there a better way of excahngin rather than in school thanks