I picked up Quercus' Autumn catalogue at the LBF and some of the highlights by British authors include:
Elena Forbes - Die With Me (see this post)
Philip Kerr - The One From the Other (previously published in the US, the fourth in the Bernie Gunther series)
Nigel McCrery - Still Waters (author of the Sam Ryan/Silent Witness books, this is the first in a new series)
Phil Rickman - The Fabric of Sin (next in the Merrily Watkins series)
Michael Walters - The Adversary (follow-up to 'The Shadow Walker', set in Mongolia)
Colin Cotterill - Thirty-Three Teeth (previously published in the US, second in this series set in Laos. 'The Coroner's Lunch' is out in June.)
Not forgetting new titles from Australian authors - Peter Temple, Matt Rubinstein and Adrian Hyland.