This was about 200ft from behind and closing, so yup, I was getting jumpy
In which case I would have concentrated on flying out of the way.
If, as you say, it was that close and closing, and you were getting jumpy, then the other aircraft must have been flown in such a manner as to cause you concern for the safety of your aircraft.
That, believe it or not, is the definition of an 'AIRPROX'.
I don't for one minute believe that sort of scenario is 'the luck of the draw'. I've flown for years at an A/G airfield where the overhead join is the norm. Never had a problem or an incident where people were behaving sensibly. The whole idea behind it is you get a picture of traffic before you join, you keep your eyes open and you descend into the circuit not, with blatant disregard to the other joiners but in an orderly queue - merging with existing circuit traffic at circuit height. If you can't see the conflicting traffic at the point of overhead entry you stay in the overhead until one of you is descending out of the way - which then decides the order.
I would dare to suggest that one of you wasn't fully aware to have this situation develop - someone's at fault somewhere.