I think we have probably exhausted the topic. I was merely trying to point out the difference between rank (which is what soldiers are paid as) and appointments (which is the job they do). Officers and NCOs had seniority within each rank dating from their promotion to that rank. That seniority often dictated what appointment they held in their company, battalion or regiment.
In the new year I intend to visit the Public Records office at Kew and try to compile a definitive table of all changes to British Army establishments during the Napoleonic Wars. I suspect this may be quite a mammoth undertaking.