I'm sure the IWM would offer a good home, and make it accessible for researchers.
Speaking as a member of the Salonika Campaign Society, had you considered making your transcription available as an article for the SCS's New Mosquito magazine?
Thanks Kate. The diary is in the UK and I am in the US (British though) so I have to get back to deliver it at some stage. I do intend on sending a version to the New Mosquito but I have to do some work on it (add references, cross reference it with the DY War History 1914-1919 and the DY War Diaries for Salonika which I have). Once that is done, I will send it to the SCS's New Mosquito. It is mostly fairly mundane, but does have a few interesting high points and is quite written well. One very interesting aspect was a cavalry charge which went horribly wrong - straight into a Bulgarian trap. It may be one of the least recorded charges of the war although on a small scale (Troop level) it is not as well know as the Yeomanry charge at Huj in 1917 for obvious reasons. it is mentioned in the War History and the Diary too.
My instincts were IWM as its resting place. Glad you agree.