The progress may well have been slow, binbrook, but every step along that road of improving the Mk1 seat would have been recorded, confirmed to be in accordance with the regulations, and could have been used to pin point any subsequent shortcomings. All that changed in the late 80s/early 90s when RAF VSOs made short term savings by issuing orders that regulatory work be suspended but signed off as complied with. Those who would not comply (usually fully trained and experienced airworthiness engineers) were sacked and replaced by untrained and inexperienced non engineers who would do as they were told, if for no other reason that they knew no better.
The Mk10 seat that killed Sean Cunningham was the result, as is the system that cannot even find the SIL that Martin Baker sent all of its customers operating that seat. Hence the overtightened shackle bolt, hence the non deployment of the parachute, hence the tragic and needless death of Flt Lt Cunningham.
The direct results of the sabotage of UK Military Air Safety during Haddon Cave's 'Golden Period' feature in all the Airworthiness Related Fatal Air Accident threads on this forum that account for 63 deaths (shortly to become 65?). The MAA that resulted from Haddon-Cave's Report still knows no better and is anyway constrained by the Star Chamber's cover up of illegal orders by its retired members.
Finally never apologise for trying to further Flight Safety, rather keep on demanding an answer. You never know, you might eventually get an answer if only to shut you up! That's my philosophy anyway, annoying though it be.