the logic that perf E was mandatory for AoC operations and advisory for private flights. Anyone operating say a Seneca in the UK on both AoC and private would now have 2 quite different sets of factors to apply, a 20 year old Perf E advisory factor for private and the mandatory Class B factors for AoC ops.
No, I've racked my brains on this one and I can't agree with the statement above. For private flights the operator has never been required to operate with any other direction than the POH/Aircraft Manual. The issue has never been the pilots licence whether ATPL/CPL or PPL: what mattered was the flight being either private or for public transport. I can recall numerous occasions when a AOC holder provided a contract of service, with the customer agreement, to provide an aeroplane and recommend a selection of pilots for the customer to choose. The customer now became the 'Operator' and the flight was 'Private. A benefit could allow the flight to take place to/from an airfield, preferred by the customer, at which AOC factoring otherwise would not allow.
For the pilot there was no dilemma: A commercial flight: then they would apply the AOC factoring in addition to the POH manual but if a private flight then it was not necessary. I cannot remember ever the CAA providing operational direction to pilots to apply the commercial factoring figures for private flights other than perhaps some few wise words for PPLs in the Safety Sense leaflet. I don't believe EASA provides anything different but if I'm wrong on that one I will need to eat my googles.