Neither of these actors has a Scottish accent. Both actors have standard 'English' accents, which is to say that that their pronunciation gives no clue as to the speaker's regional origins. In fact, Nicol Williamson WAS a Scot, but he did not speak with a Scottish accent. Rob Inglis was originally Australian, but he also speaks in a completely neutral, standard accent with no trace of his origins. Both these men were born in the early 1930s, which means that they have the distinctive 'clipped' pronunciation of British actors of that generation. Perhaps this is why their manner of speaking was unfamiliar to you. By the way, it makes no sense to say 'not in a British accent, rather in a Scottish accent', because Scotland is part of Britain. There are many different British accents, and among them are various Scottish accents. I hope that makes sense.

Well, flicking through the the videos it seems they change their accents to reflect the different voices of the characters throughout. For example, in the second clip at 1:31:40 the guy adopts a Scottish accent. But when he is just narrating the story, he has an RP accent. As for the first guy, if he's not English then I would say he has clearly spent a lot of time in England. I say that as I don't what his background his and I can hear a slight Antipodean influence there. It wouldn't surprise if the guy was originally from Australia or New Zealand.

a shorter sample of Williamson's record : https://www.youtube.com/watch?v=5nphDlbR4bY&list=PLvLOuNp3Ksj1OkAfCSA0s5J17zirlvR63&index=1

Rob Inglis : https://www.youtube.com/watch?v=XeOVIwEgLBQ and I'm searching for a sample of Williamson's record

Do you have smaller samples? Both of your youtube links are several hours in length. You can take a short extract and upload it to vocaroo.com