Was Andy Serkis's portrayal of Gollum inspired by John Byner's portrayal of Gurgi?

The Internet abounds with speculation and unsourced claims that Andy Serkis based his performance of Gollum in the Peter Jackson films on John Byner's performance of Gurgi in The Black Cauldron:^1,2

Of course, even before the films, literary scholars and critics had remarked upon the commonalities of the two characters as written in the source novels, particularly with respect to their speech patterns.^3,4,5 And while it should therefore not be surprising that any two actors' interpretations of the characters should have some similarities, the resemblance of Byner's voicing to Serkis's is uncanny—far more so than it is to other portrayals of Gollum, such as those of Peter Woodthorpe (in Bakshi's Lord of the Rings) and Brother Theodore (in the Rankin–Bass Hobbit).

I know that Serkis has said that his portrayal was inspired, apart from Tolkien's writings, by the sound of his cat coughing up a hairball. But I am wondering whether that is the whole story. Has Serkis himself, or anyone else involved in the production of the Peter Jackson films, confirmed or denied that his portrayal was inspired in part by Byner's Gurgi? Has Serkis at least commented on the resemblance?

_References:

_{1. "Gurgi". Wikipedia, accessed 28 August 2019.}

_{Gurgi's performance in the animated movie would go on to inspire Andy Serkis when portraying the Lord of the Rings character Gollum/Smeagol in Jackson's rendering of the books by Tolkien, both in the Rings Trilogy and the prequel trilogy around The Hobbit.}

_{2. "TIL that the voice actor for Gollum, Andy Serkis, used as his inspiration the voice of Gurgi from Disney's "the Black Cauldron" movie, listening to him talk is really eerie! This clip sounds exactly like Gollum!". Reddit, r/lotr, accessed 28 August 2019.}

_{3. Patterson, Nancy-Lou (1976) "Homo Monstrosus: Lloyd Alexander’s Gurgi and Other Shadow Figures of Fantastic Literature," Mythlore: A Journal of J.R.R. Tolkien, C.S. Lewis, Charles Williams, and Mythopoeic Literature: Vol. 3, № 3, Article 9.}

_{Readers who have noticed Gurgi's Gollum-like speech habits will not be surprised at the nature of his appetite… One thinks of the Gollum/Sméagol conflict in The Two Towers. When he eats, Gurgi's delight is fulsome: "Gurgi, sitting cross-legged, devoured his food with so many outcries of pleasure and loud smackings of his lips that he seemed to be eating twice as much as he really did."}

_{4. Sigman, Paul (1971). "The Book of Three" (book review). Mythprint, Volumes 3–4.}

_{[Gurgi and Gollum] seem to be similar, scurrying creatures—they even have similar idiosyncrasies in their speech patterns…}

_{5. Fisher, Margery (1975). Who's who in Children's Books: A Treasury of the Familiar Characters of Childhood. Holt, Rinehart & Winston.}

_{In appearance, and in his utterances, Gurgi is in some ways not unlike Tolkien's Gollum.}