The CAA seem to follow the letter of the JAR law, or that was certainly the case with me. During an ultrasound the doc found three tiny gall bladder stones floating around inside me. I believe one of these little devils was the cause of a very uncomfortable bout of indigestion (as I thought it was at the time) and, small wonder, Gaviscon never did any good
Anyway, I haven't had any repeat episodes of the 'indigestion' but, for obvious and good reasons, the CAA got a copy of my ultrasound report. They sent me a letter detailing JAR Ops blah, blah, blah; the long and the short of it being, more than one gall stone = a note from the teacher on one's medical certificate saying 'with or as a copilot' (or somesuch wording). It makes absolutely no difference to an everyday airline pilot but I can appreciate it may to someone who hasn't yet got to that position. And, just to clarify, that was only for Class 1 privileges. Flying around on the PPL makes no difference.
So, it sounds like, even with a 7mm stone, if it's by itself then there should be no restriction placed on your Class 1.
Small print: not written by an AME or someone purporting to be one!