In my opinion nobody came close to filling Denny's shoes - as you said, a different class.
Denny also acted us unofficial 'arranger' on the Donegan recordings he was involved with and his creativity on 'Don't You Rock Me...', 'Cumberland Gap', 'Dead or Alive' and a few others wasn't limited to just his tremendous guitar playing. Those tracks are what elevated Lonnie to the point that he had no real competition in the skiffle genre - the other groups were rank amateurs.
However, I have to say that I'm unaware of any footage showing Denny with Lonnie's band. He played for Donegan from mid-1956 until Spring on 1957 (arguably LD's most important musical period.) True, Denny did return to the band in, I believe, 1962/3 but by then the magic was over and nothing of importance came of the later association.
The 'Putting On The Donegan' shows (1959 onwards) all, as far as I'm aware, feature Les Bennetts. Les replaced Denny's successor, Jimmy Currie and, in my opinion, Denny, Jimmy, then Les represented an ever-downward spiral in the band's musicality.
If you do find footage of Denny with LD in his earliest stint with the group I for one will be absolutely delighted but I fear there is none.