He is right about big business in a way, but remember without all the large companies like Dr Schar, Juvela etc, we just wouldn't have the type of GF food you see now.
I don't touch codex products myself, and have personal doubts about their suitability for a GF diet, but I don't have a problem about them being available, and there are plenty of prescription items that don't contain codex wheat. I think the issue is whether prescs. are a cost effective treatment for a disease which has invisible, long term health implications if not treated by diet.
Personally at a cost to the NHS of about £98 per diagnosed coeliac, I don't think it's bad value. People can chose not to have food on prescription, but for those families that actually need it, help with GF staples is important.
I don't have a problem with some of Dr Cave's views, and I actually agree that the NHS scheme is not suitable for purpose. The need is still there, we should just find another way to make it work more efficiently.