If you are so inclined, perhaps you would be interested also in sending out brief and polite inquiries? I do not think that short, politely worded letters do any harm at all, and there is a tiny chance that the right question posed to the right person at the right time might just lead to a happenstance recovery.
Happy hunting! By the way, when at those film collector meets, besides looking at the film prints themselves, please don't shy away from talking with as many people as possible about the missing episodes or old TV prints on 16mm. The recovery of the print of The Lion and the recent find of the Metropolis print in South America both resulted from a random clue that arose in conversation. Someone may know a friend who knows a friend who knows a friend who supposedly has some old black & white TV shows on 16mm, and that sort of lead can potentially result in a recovery.
Have sent snail mail enquiries to the Brunei and Laos archives. Will send to the others when I get the chance. Not getting my hopes up - even for a response - but it's worth a shot. I've also included the URL for www.missing-episodes.com in case they have anything from other missing programmes.
Thank you for your valiant attempts. This is can be categorized in the file of 'nothing ventured, nothing gained.' I am firmly convinced that if there are any more missing episodes out there to find, they will almost certainly be found because someone asked the right person about them at the right time.
For all we know, some archivist in Laos might reply, "Oh, do you mean these prints of 'Web of Fear'? These have been sitting on the shelf here for thirty-five years!" Something along these lines will take place if and when another episode finally turns up.