Try to get hold of that 'Jazzwise' DVD of the Collier band at the Derby Fest a few years ago, in a lineup in which Harry Beckett is prominently featured. About 20 minutes of the disk (which covers what was on at Derby that year) is of the Collier band. I'll be digging it out today.
Also - to get a better feel for the later works Jazz Library on BBC Radio 3 currently has the full Collier interview up for listening - essential stuff.
Will be putting in my order for the new BGO compilation. All of those are really fine - good sound and very informative notes.