Sorry to blunder into this thread late and also far removed from any detailed knowledge of the case in question.
Possibly part of the "military aircraft mid-air" speculation came from, IIRC, the recovery of a nosewheel leg and some bits from what some in the the popular press at the time deemed to be an "RAF Fighter" , during the investigation.
Again ,IIRC, these bits turned out actually to have been from a Meteor which went in many years previously.