After nil response to my own post a few days ago re iron-related blood tests (unsat. iron low, folate high, transferritin sat high) and reading others which indicate serious confusion, I conclude that there is a total lack of clarity. Maybe this explains why my GP is unconcerned by my out-of-range readings (according to receptionist only!) or maybe it's because of interaction by other things e.g. I was taking B Complex when tested which I subsequently read is not advised.
Happy to share my results if anyone is interested in trying to solve this confusion!