Probably just as unreliable as any other list but there was a news story recently about possible discoveries so just in case...
Galaxy 4 Ep 2
The Myth Makers Eps 2 & 4
The Smugglers Eps 2 & 4*
The Highlanders Ep 2
The Space Pirates Eps 3, 4 & 5
*Interestingly "The Smugglers" was rumoured for an animation a while back, which sounded odd as historicals tend to sell poorly.
At least the ocassionally-mentioned "The Tenth Planet 4" isn't included in the list, nor are other fan-favorite stories as low-hanging fruit.
Even if someone had films in a basement or attic - those will not lose value just because they were digitized and repaired. The actual artifact is 100% unique and irreplaceable. Real history. Any one of us has probably bought a recreation of some piece of pottery circa ancient Rome, or even a calendar with a crisp 35mm print of said pottery (with all the fun bits showing and all!). The actual piece in the museum didn't lose any value as a result of photos or replicas made. Why would it be any different for a piece of film?
Ditto for the filmed inserts for "The Two Doctors", held by a private collector and likely for the same cause and reason*, who refused to lend them out to be digitized for the blu-ray release.

Whether they actually still exist or not, however...
* correlation not always being related to causation, but that's a given
It's interesting that the episodes in question are predominantly from the latter half of the historical range, plus "The Space Pirates".
The following links go to articles where said episodes were sold to:
https://broadwcast.org/index.php/William_Hartnell_stories
https://broadwcast.org/index.php/Patrick_Troughton_stories
Since not all films would be duly returned, some were abandoned, some taken by collectors, some junked in their destination countries (but possibly a dumpster diver found something cool and kept it), or so on. Even those that were returned and dumpstered could easily have been saved by a private collector.
IMHO, Galaxy 4, Highlanders, and The Space Pirates hold the most potential interest.
I've a feeling "The Space Pirates" has a bad reputation because the sole episode in known existence is a bit rubbish (even with one lazy visual effect, where getting the polarity of the large magnets wrong hurls the base's segment in the wrong direction (toward and through the others, not the other way, oops.) The Enemy of the World and The Underwater Menace both had reputations of being rubbish until other episodes were found and returned. Both their respective part 3s were clearly filler and padding; the newly-recovered episodes of those stories containing actual plot build-up and character development and were surprisingly marvelous and a joy to see.
Galaxy 4 ep 3 shouldn't have been as entertaining as it was, but it works...
Highlanders remains a curiosity.