Thanks very much for your reasoned response. I like you, have found so much conflicting information regards L-Glutamine. I think my issue is that I am not entirely convinced I have Candida and that it may be leaky gut. In my experience it is just a complete lottery with regard to supplementation, but this is the worst I have felt for some time.
I will stop using the L-Glutamine for a few days and see how I react.
With regard to Candida (or whatever this is in my case) being caused by some sort of stressor - I am in agreement with you here. I have often thought that it may have developed from a bout of gastroentiritis I experienced about 10 years ago which I had again a couple of years ago. I'm sure it strikes some sort of inbalance that is hard to put right.