The Doctor Who restoration team has used ultra-sonic cleaning on the recovered film reels of missing episodes. These are B&W prints from the mid 60’s so a bit older than than film prints being used here and definitely with vinegar syndrome. It is safe and very effective. The results have been amazing. Definitely worth the time and effort for the OT prints.
Indeed they do. When they got Web of Fear and Enemy of the World back in 2013, they already had a superior copy of Enemy part 3 in the archive. So they tested out the ultra-sonic process on the duplicate print as a test to make sure the prints that had been sitting around in Nigeria for 40 years would not be damaged by the process. After comparing a short stretch of the film before and after cleaning, they determined there was no damage.
They recorded some of the prep and transfer, ultra-sonic at the 2 minute mark: https://www.youtube.com/watch?v=nsMgNCwYcXw
It would be interesting if they could try the process out on the copy of The Lion (Crusade episode) owned by that Australian collector. I think most of the print’s problems are from actual damage, but it might be dirty as well. I don’t think they’ve gotten a chance to re-scan that one since 1999.