Dear Mr. Murray,
Thank you for posting your request on History Hub!
In case he was involved with the Office of Strategic Services (OSS) while in MI6, we searched the OSS Personal Name Index but were unable to locate a listing for Thomas W. Murray or Thomas William Murray.
Since he was in MI6, any records concerning him would be in the custody of the British government. We searched the website of The National Archives of the United Kingdom and located their research guide titled How to look for records of Intelligence and security services. If you have further questions, please contact the UK National Archives via their website.
We hope this is helpful.