Thought it would be handy resurrecting this to some things lost over the last 30 years..
I remember Eurodirect, they operated a wide number of services from Humberside using Jetstream 31 and ATP equipment. They didn’t last long, but the BRU service was retained for quite some time under Eurodirect Belgie which I think was double daily on a J31 with Sabena code share. Believe it lasted a couple of years after the demise of Eurodirect and itself ended in around 1996.
Citybus operated a short lived HUY-LCY service multiple daily on a DO228, think that lasted months rather than years and was in 1994.
Air U.K. operated to LHR multiple daily on S360, service ended in 1992 when LHR increased costs.
Gill Airways operated a 2x daily HUY-CDG on ATR72 in full Air France livery. Initially shared with MME, the MME leg was dropped. Lasted at least 18 months and recall did well.
Ryanair in 2006 daily Dublin service. 4500 to 6000 passengers a months, pretty good figures where it not for the fact that it was a B737-800! Also competed directly with DSA. Dropped after In 2011 ran a 2 x weekly ALC service with high load factors (higher than DSA), dropped after one season due fallout with ALC.
FlyBe ran one season of flights between HUY and AGP. Very high load factors but they never returned.
Excel based an aircraft part of the week in 2006, plans for a full based aircraft and a second part based aircraft for the 2007 season never materialised, clearly their financial standing wasn’t great and we know what happened thereafter.
There are a load more examples of charter destinations, perhaps people could add to this list.