OH my gosh! Do not eat Quorn! I did eat Quorn and had a very violent reaction. I have never been so sick in my life with protracted vomiting. I was in such a bad state that after I recovered I researched "Quorn complaints" and found there were many complaints of severe allergic reactions and there was a class action lawsuit against them. Mycoprotein is, the end result, not really mushrooms or food. It is manufactured and, as Debra says, not found in nature.
There is a web site somewhere that you can report your symptoms/reactions. It's best just to stick with what nature has provided. I have been a vegetarian for almost 30 years and there are lots of choices out there, but mycoprotein should not be one of them!