Numbers....
Breadof Heaven is putting everyone's lists into a spreasdsheet, so he could probably tell you the Composer with most different pieces, and the composers and pieces with them most votes.
For what its worth, my favourite composers are Peter Graham (Harrison's dream, The Essence of Time, On Alderley Edge, Montage), Philip Sparke (Partita, Celtic Suite, Harmony Music, London Overture, Kaleidoscope) and Eric Ball (Journey into Freedom). They've written too many pieces to write them all here! You can get lists of pieces by composer on the Just Music website.
http://www.justmusicuk.com
Go into the Brass Band catalogue, click on FIND (2nd valve from the left!) and put someone's surname in the "composer" field.
Just had another thought - I'm sure if you asked Philip Sparke (Anglo Music Press) or one of the other composers on tMP
very nicely for some information about themselves/their music they'd help you out.