Now if you are a UK anime fan of a certain age you likely have something vaguely resembling fondness for the 1987 OAV adaptation of Go Nagai's manga. This however is the 1972 TV version of the story. And as it was created before/alongside the manga there is significant differences in plots. In particular unlike the manga or OAV there isn't a Ryo Asuka character. And if you've seen the terrible Amon: The Apocalypse of Devilman OAV, are familiar with the events of the later Devilman manga volumes or the Violence Jack manga then you'll know that single omission is a big difference.
And… the first six episodes have been fansubbed.