being child free today and needing a cheap lunch while shopping we went into a wetherspoons. The information on the menu was quite good -food that contains nut is labelled and they also have a symbol for food that is safe for coeliacs. They are honest about not being able to guarantee there is no contamination.
If you are caught in a place you don't know and need to eat out there could be many worse places. (food wasn't brilliant btw - cheap and cheerful).