IMDB have this down for release on November 15th and MK as the composer of the main theme. It maybe that is it only one song from him and the rest Evelyn Glennie (who I'd never heard of before this).
If you believe Guy and MK himself, the score is by MK, with help from Evelyn Glennie. Guy mentioned in his forum, mainly as answers to my questions, that he and MK were working on music libraries for the score, that Guy himself went to Glennie´s studio to record samples of percussion instruments before she went to BG, and I read in some MK interviews that he apologized with the interviewer about being late because the Altamira film director shot more parts for the film and some more music was needed...
And I also read that the director of Altamira is MK´s friend, so, I guess that the score is, at least by MK and Evelyn Glennie, according to everything I read. Maybe Guy can be asked about this by someone that is not me for a change