It isnt so much that the commercial kitchens can't provide appropriate food, it is that they cannot give you an absolute iron clad guarantee against contamination. The nature of a catering or resteraunt kitchen makes such a guarantee impossible. It is very likely they can provide a safe meal, but they cannot guarantee it. Now that your DD is big enough to be out in the world, dealing with her allergy will be a constant habit, and you are going to have to become risk assessors. Sometimes, if you must be away from home, you can take a supply of safe foods and whole foods that will last until you get home. Other times, you have to read the menu, understand what foods are more or less risky, ask to see labels of products and ingredients, ask questions, and then order the best bet, and have the epi-pen in reach.
My 3 DN were allergic to peanuts, treenuts and soy, in various combinations between them. For my DB and SIL this meant a lot of cooking from scratch at home, stocking the freezer with things like biscuits and savory snacks and ready meals and homemade sauces. It meant staying in a holiday let instead of hotels (still risky, but better) in order to cook/have a frridge freezer for foods from home. It meant trusting that relatives understood the allergies and understood how not to cross contaminate. It meant sometimes depending on meals made up of fresh raw fruit and veg., plus cheese or yogurt and either brought from home or packaged products like crackers or bread they had learned were reliably safe.
For the packaged products, they depended on an online network of parents who contacted manufacturers to research and confirm allergen status of products. They are in the US, but I am sure there must be a UK equivalent. Probably there is an MN forum! Some crackers, biscuits, soups etc are reliably allergen free because the company makes nothing with those allergen. these are often expensive and 15 years ago were often only available through fancy grocers or health food stores, or maybe at large suburban stores, vs. the smaller rural store he had easy access to. Sometimes, because of the manufacturing sequence, a product without allergens is still a risk because produced after an allergen containing product. The production line is clean, but there is still risk of cross contamination somewhere in the building. It might be as minor as the products being stored in the same warehouse as nuts. There is always the chance a worker reused a scoop or bin, or even just handled a bag of nuts then a bag of flour.
But sometimes, due to a change in sequence, the product is is run on a completely clean line in a building that has also had reason to be completely cleaned, and word goes out on the internet of those stock numbers. Parents across the country hunt to see where that run of products was shipped, and buy as much as possible. Then, they swap. My brother regularly had things like 10 cases of pasta sauce in his garage, which he gradually swapped for cases of biscuits, soup, salad dressing, or whatever.