BOAC There was a time when I went through hundreds of pages of documents and memos. I don't recall the BOI or AAIB referencing any of the Boscombe Down memos including the ones about ceasing flying. The MoD now says the documents were "available" but not in practice - the BOI had to know what to ask for.
It may also be worth pointing out that the BOI did not reference - and there's no evidence they knew of - the Wilmington incident in which a Chinook on test was damaged by a Fadec-related overspeed. The MoD was suing Textron Lycoming at the time of the Mull crash. This wasn't known about until years later.