Crome Dome,
Are you aware that, in addition to the memorial referred to above, the crew will be commemorated at the Armed Forces Memorial at Alrewas, Staffordshire and within the 'on line' Roll of Honour. This latter will show details of his age, service number etc.
It might prove a little difficult to contact the RAF witness directly. This will be for a variety of reasons such as the person is no longer serving and there is always a reluctance to give out such information.
You could try contacting the Joint Services mountaineering association (don't not what its real title is) as they will probably have a magazine and may have an archivist who could help. Another approach might be to write an open letter to this unknown person and then ask the Army Air Corps if they would forward it to the RAF Personnel Disclosures Branch at Cranwell with a covering letter explaining that the letter should be sent to the RAF engineer, whose name the Army Air Corps will know from the Board fo Enquiry proceedings (GOSH that reads as very long winded).
Old Duffer