During my researches on another topic I came across a letter by Sir Arnold Hall (chairman of Hawker Siddeley Aviation) following his visit to Egypt in February 1972. He was given a tour of the Helwan plant.
He states at that point the plant was basically making MiG-21 drop tanks. He describes it as "Its tools are rather out of date - the plant has gone to seed, though very large sums have been spent on it in the past.
The Soviets had offered a MiG-21MF licence but the EAF seemed reluctant to build them, wanting a fighter-bomber which the Soviets refused to supply.
He describes the engine shop as being more active but still of limited capability. He claims he was shown "two engines of their own" which he said looked like copies of a French and a Russian engine. Presumably these must have been one of the locally-built Marbores for HA-200 and the Brandner E-300 (Brandner had worked in the USSR before his release in 1953 so its possible this is why it seemed "Russian" to Hall?).
Hall goes on to claim only 35 HA-200s had been built (Flight a few years earlier had estimated 65, Wiki states 90 - not sure what the real figure is?)
Of the HA-300 he says "had never flown, but recent orders have been given to prepare it for flight." This must refer to the 3rd prototype as of course the first two prototypes had flown a decade earlier. Given that the HA-300 project was terminated in 1969 this resurgence of interest in early 1972 is interesting as is whether the engine was still the intended E-300 or something else.
He noted there seemed to be no provision for any armament.
Hall goes on to say "Discussions revealed that instructions had been given to adapt it to a fighter-bomber role, under the number Cairo-400 - the airframe seemed unsuitable for such adaptation. I think little progress had been made with this task."
I have not come across the Cairo-400 designation before (in his letter the Helwan aircraft are referred to as Cairo-200, Cairo-300 and Cairo-400) and this seems to be a little-known further development, probably one that was short-lived.