Grunt
RACAL did produce a report on the SUPERTANS fitted to ZD576, but I have never seen it and as far as I am aware it is not in the public domain.
The report is widely available. Give me time and I'll PM a link. However, Commercial-in-Confidence parts are not available.
The main issue here is that Racal "tested" the remnants of the RNS252 and said "It worked". Then MoD took the extraordinary leap of faith by claiming this meant the entire Nav System was both serviceable and accurate (despite, as above, most of it having no clearance as installed performance had not been established - which means you have no baseline against which to measure ZD576's performance).
They also conveniently forget that while a "black box" may be serviceable, that in no way means the indication to the pilot is correct; and, more often than not, that indicator is not part of that installation. For example, the Radar Altimeter (which in ZD576 carried both defects and faults, making a mockery of MoD's claim the Nav System was fully serviceable). .
In short, the aircraft was immature, at best still in its training and development stage, and operating against a wholly fabricated RTS.