All very good points, well made.
What I was really getting at when I mentioned going around at 500' is that in this particular incident, caution needs to be exercised by the OP when corresponding with the aero modellers. If the PFL didn't breach any rules then fine, but if was flown lower and the aero modellers report the incident things might get unpleasant.
It is impossible for the CAA to determine how high the model aircraft were flying, however easy for them to view a radar replay or for someone on the ground to have taken a photo that could be used to determine the height of the full size aircraft.