It's a tricky question to answer honestly as anything to do with health is always emotive isn't it.
I personally don't think the NHS should pay /cannot afford to provide gluten free products. I believe we have to take responsibility for what we eat , know what you can or cannot digest to safeguard your well being. If there were no gluten free products available then it could be viewed differently.
It is like asking if an alcoholic should get free alcohol, should an obese person be provided free health food, should somebody with a lactose intollerence be given extra funding, the list goes on.
Why should the NHS provide funding across the board irrespective of financial ability to pay. Some people on a lower income choose to purchase less food but buy organic for example. What we provide for our well being is our responsibility. Some of us can't take dairy products, some sugars, some gluten.
It is all about food labelling, knowledge of the right and wrong foods you can eat, gluten free foods being just one issue that arises. Food labelling is essential. The NHS has a duty to discover when there is a problem, a duty to inform patients how to handle their illness but from that point the NHS cannot fund that lifestyle when it is available over the counter or requires preperation by the patient to maintain their health.
I have a friend who is gluten intollerent. She is hardly hard up and knows what she can or cannot eat. I believe I am right in saying one ice cream manufacturer she can use but not another, one gravy ingredient is suitable but another, she makes her own bread. etc. Why should the food be free and provided by the NHS.
I hope I have not caused offence, I understand the difficulty of a gluten free diet and it is only a personal view.