When television companies buy films to screen on television they often get rights to screen them several times and usually pluck for more popular films.
In the early days of Channel Four, a single film screening would expect to catch a greater share of the television audience than it would today so it was less expedient to repeat films. It also costs less per screening to prepare a film to screen several times.
Often television companies deal with the same rights holders and this often leaves smaller distributors catalogues untouched.
With the advent of satellite television, some opportunities have arisen for smaller companies to sell television rights to companies who need to fill screen time with non-commercial product of interest in order to gain a decent slot for their shopping channels. This is how we got to see so many films from the Renown catalogue recently.
Perhaps if more companies go down this line, we may get to see other obscurities unearthed.
Let us know which films you are thinking of and I will look to see who holds distribution rights.