I recently went on a trip to Canada and they allow you to bring in a good amount of produce. Just be sure to check with the UK customs website on the limitations before you pack. Then pack a bunch of vegetables and other snacks that are allowed on the diet. For your liquids, you could make a match of salad dressing to bring with you, just make sure it’s under the restricted amount, or you may want to carry on your luggage. As kodaz2005 mentioned, you need to eat at restaurants where they actually make the food, then you can order specific ingredients. A lot of restaurants have gluten free menus which match the diet a lot of times. You could also visit restaurant websites in the area you’ll be staying before you even leave so you can already know what you want to get. Ask for a room with a fridge and go grocery shopping once you get there. Good luck and have fun! Don’t pass up the trip because of the diet! That would be a life not worth living.