Back about 1982 or so, there was a bookstore downtown that had a huge selection of these. As they were about to change location, they had most of their stock on sale, including the Pan horror books and the Fontana books of horror and ghost stories (they didn't have any of the Pan ghost books). I managed to pick up what they had for about $25 U.S. which, at the time, was the majority of each set.
Sadly, due to various reasons, I only got around to reading a handful of them at the time, and several years later the bulk of those went elsewhere during my divorce. I've not been able to find them for an affordable price since.
But I do recall being impressed with the contents overall, and thinking what a very good introduction to a wide range of both classics and contemporary work in the field these were....
On the Fontana books of ghost stories, I recall that the first several were edited by Robert Aickman, though I'd have to look up how far into the series that was....