Babs: This underlines my point. There is no C Class on LHR-EDI flight. It is a one-class aircraft.
A 'C' fare is a fully-flex fare. An 'M' Fare is a restricted fare.
You are confusing fare basis, class of ticket and class of service.
Gardener, will have had an 'M' fare, with a 'C' class of ticket but 'shuttle/econ' class of service.
This is because there is no real C fare in Europe.
Confused?!
Nick