I started watching when Tom Baker was the Doctor in the 80s sometime. It was on PBS here in the states, I watched up until Baker's tenure ended. Shortly after that it conflicted with ST:TNG and my parents liked that more than The Doctor. My favorite companion always has and always will be Miss Sarah Jane Smith (currently my desktop wallpaper made by an artist right after Liz' death) followed by K-9 and the other tin dog Micky. The reason why it is so hard to find all of the episodes is because they were destroyed. As new episodes are available it is because fans have come forth with them on VHS and other media. Much of the library was lost many years ago.