Can you name the musician who 'introduces' the various musical instruments on Mike Oldfields album Tubular Bells and also the actor who does the same job on Tubular Bells II ?

Viv

Vivian Stanshall and John Cleese?

Viv Stanshall was the voice on the original Tubular Bells but it wasn't John Cleese on the 2nd album.
Viv

Wow ..never knew that!
It was Alan Rickman on the second album.

He is one of my favourite British actors. I think "Truly, Madly, Deeply" has got to be in my top 20 list of movies.
Link to Wikipedia forTubular Bells II

Alan Rickman.

And who could ever forget Stanshall in 'the Intro and the Outro' for the Bonzo Dog Doo Dah Band, where they take the mickey out of jazz combos of the era: " Here's J Arthur Rank on gong !" ?

Well done dancegirl and Fred, Alan Rickman is the correct answer.
Once again dancegirl we seem to agree on films,Truly Madly Deeply is one my favourite movies also.Makes me laugh and cry in equal amounts.
Probably the best thing I have ever seen on stage,certainly the most memorable, was Alan Rickman and Lyndsey Duncan in Christopher Hampton's adaptation of Les Liaison Dangereuse in the West End. He was totally mesmerising,I know John Malkovich is much praised for his part in the movie,but he pales compared to AR in the same role.
Viv