I currently have gastritis, esophagusitis, stomach ulcer and can't touch acidic foods. I'm struggling with sauces for my diet, what can I have (tomato sauce, mayonaise etc). Is gravy ok? Also what crisps can I have that don't contain gluten?
Stay off tomato !
I'm ok with gravy I don't eat mayo so don't know about that
chew gum try almond nuts .
also I find soya milk helps you can try different flavours seems to calm acid attacks!
crips I'm ok with but if you balance your diet and counter balance your comfort foods with foods that help against burn google them and apply what you can where you can ( for example I use soya milk on cereal but stay with milk in tea  
trail and error but look up foods good for reflux
Mark you are going to be a lot stricter with your diet. About tye worst thing you can swallow with a very sore throat sadly is crisps. You can bake kale for 8 minutes with olive oil and salt. Tasty and super healthy.
I would stay away from tomato sauce as that is a no no (too acidic). I must admit I make my own dressings now and it is more gentle on the stomach. Depends what food you are eating it with but here are a few of my tips (all based on greek yoghurt and a tiny drop of olive oil plus any of the following).
Garlic, fresh cucumber or mint, avocado, pesto, fresh beetroot, small qty of wholegrain mustard.
It works for me and is much healthier (and fun experimenting)