A bit of info / news about MOD records whilst it refers more to the RAF it does i think help to explain just why we are having difficulty getting the info we need on the St Venant thread.

Defence Business Services (DBS) has begun the transfer of Second World War RAF Casualty packs to the National Archives.

The packs were produced following an incident involving the loss of an aircraft or personnel and include the report of initial loss, correspondence with the next of kin, any further information received on the incident and any subsequent correspondence with the next of kin.
A limited public consultation was held in 2012 seeking the views of interested parties regarding the remaining sensitivities surrounding the packs, and there was widespread support for the release of the packs.
There are approximately 56,000 packs in total and DBS plan to review and prepare about 8,000 of them by 31 March 2014.
The first tranche of 316 packs were delivered to the National Archives at Kew on 28 October 2013.

"I am delighted that the first tranche of these historic records have been transferred to the National Archives. Although the focus of the DBS records team has been on reviewing and preparing the department’s records from 1983 and 1984 against the requirements of the 30- to 20-year rule change, we are equally keen to transfer remaining World War 2 casualty records, and this delivery represents a first step."

The first tranche of packs covers the period 4 September 1939 to 13 May 1940 and includes those related to the raid on the Albert Canal Bridges on 12 May 1940.

"The RAF casualty files detail the losses of the RAF in the air, at sea and on land. Many human interest stories abound in these files, from the kindness of villagers to downed airmen to the unique work and testimony of the MREU (Missing Research Enquiry Unit) set up in 1944 to trace many thousands of personnel who were listed as ‘missing, believed killed’.
"These files are a fascinating and valuable historical resource, and it is a great privilege for the records team to be able to review them."

Obviously i have removed names for reasons which i am sure you will understand, It does show there is still a lot of records relating to casualties not yet on general release to the public and i suspect the ones needed for the St Venant thread may well come under this (see the comment in bold) for a possible explanation of our problems.

I hope this may be of some use to someone in due course, apologies if this is out of order.

Dave