...he was going to report him.
Report him for what? Flying VFR? See and be seen? Being seen but not seeming to see himself?
Maybe in the UK everything is different again, but in my part of the world, you need to be inside a control zone orn an ATZ in order to be protected from other traffic while doing your traffic patterns. As there are currently no ATZs in my part of the world, every airfield without a control zone must be considered open airspace. Of course it is not the best airmanship to fly through traffic patterns at or below pattern height, but it ain't forbidden.
My most impressive experience like the one you had was an American B52 flying right through the traffic circuit of an aerodrome where I was practising landings with a student. Luckily he was slightly below pattern height so we didn't get into his wake turbulence (almost certainly lethal for a C152 at 1000ft AGL) but got away with an "incipient heart attack" instead... When I asked the radio operator if he had seen that monster, he replied "never mind, they do that all the time, complaints are useless".