for a start try the book 'The Cold War Years - Flight testing at Boscombe Down 1945 - 1975 by Tim Mason. ISBN 1-902109-11-2
Failing that try the folk at the Information Warehouse, QinetiQ, MoD Boscombe Down, Salisbury Wilts. SP4 0JF. Who are custodians of all the A&AEE reports.