Thought I'd start a thread on Piatkus, one of the UK's major independent publishers, with some big authors such as Nora Roberts.
Most important: they do accept submissions from authors directly.
I remembered them when, going through my email folder, I found a rejection mail from one of their editors from December 2005. It was a very helpful rejection, with complimentary comments and giving the reasons for the rejection, and an invitation to submit other work.
Just recently, they have been taken over by Little, Brown but will remain an independent imprint.