Billy Mahonie were a London based all-instrumental band; the brain child of Gavin John Baker. At the time of this single, their line up consisted of two bassists, a guitarist and a drummer. Their music was always labelled post-rock, I guess partly because of the lack of a singer and because they were contemporaries of bands like Tortoise and Mogwai. I'm not sure that either comparison is that helpful; whilst they could certainly play it loud, they were never quite as bombastic as Mogwai can get and unlike Tortoise, there's no black-polo-neck-and-goatee-beard-jazz thing going on. What you do get is rather lovely interplay between then guitar and basses, fairly sparse drumming and a sound that shifts effortlessly from quiet and intricate to loud (and still intricate).
This was their first single proper; they'd previously release a split-single with fellow bass guitar over-users Rothko on Fierce Panda; this came out on Fierce Panda offshoot Livid Meerkat, in 1998. You can hear both tracks from the single, On The Brinck and Whistling Sam, at Gavin John Baker's excellent and exhaustive Bandcamp page, on the very fine Found compilations.