Some car boots dont allow the selling of food and drinks except for the Catering van.
I sell at Tynemouth market and there are a number of cake stalls there none of which display anything at all about licences or certificates. I know at least one of them makes the stuff at home as their Cafe went bust. I do think if the council inspectors came round though they would have a field day with how the stuff is stored never mind where it was prepared.
Edit see others have answered more knowledgeably before me.