I am not sure if a torrent is legal in a situation like this with non-broadcasted episodes, however; there was a complete download of all the seasons into the 80's prior to the release of the 'New Doctor Who'. I have seen many of them as reruns as a child, but someone at one of my jobs had a huge portable drive he'd share with others. It was like 300GB or something crazy.
If legal that would be an option, if illegal you will have to search high and low for legal downloads and collections.