Hi. It's a very interesting question you asked. I hope no one minds that I am posting a reply that doesn't really contain an answer...and I am certainly not writing to contradict what anyone else has said. I looked in my two Cliff discography books and for Sing a Song of Freedom, it lists separate credits for the "single" and for two or three live concert versions of it that are published on various albums (ie, Help It Along album). One book simply lists the Brian Bennett Orchestra for "all music" on the single. Not very helpful. And for the live versions from the concert albums, it says all the names that you all have already named.
Here is a video from 1974 that says it's from the London Palladium. Sing a Song of Freedeom is the third of three numbers that Cliff is singing. Specifically, if you move the "time bar" to about 8:40, you can sort of see the acoustic guitar player in the front row, center, of the orchestra. Alan Tarney is next to him on bass. I think this is Kevin Peek, but I defer to those of you who would know better than I would whether this is Kevin. But this really only says who was playing the acoustic in 1974, not necessarily who it was in 1971.
I am fascinated when I look back at old videos that I'd seen before...but when I look at them now, I start to recognise all the people in the background. Before I became a Shadows fan, I was only looking at Cliff. Now, it's almost that I'd like him to take a few steps to one side so that I can get a better look at the band.
Kind regards,
Donna