I am a student from Czech Republic studying in the UK. (so I´m an EU citizen)

I would like to start my own small business here and would like to know what should I get before I start and how hard it would be to get those things. It´s not a huge business. I love baking and as I lived many years in the USA I´ve learned how to make amazing donuts to eat. I would like to make them and go to the streets of Birmingham where I currently live and study and sell them. And I would like to know what is necessary to start something like this. I would like to try to sell like a tray of 40-50 donuts in one day so it would be really small. I don´t really know what things do I need if there is any license I need and things like that.

Thanks for any help.