From Authors On Line Workshop, these UK publishers accept unsolicited manuscripts:
Legend Press
e-mail: submissions@legend-paperbooks.co.uk
http://forward.legendpress.co.uk/paperbooks/writing-competition-a-tale-of-two-halves.html
Tindal Street Press
e-mail: editorial@tindalstreet.co.uk
http://www.tindalstreet.co.uk/
Choc Lit Publishing
e-mail: submissions@choclitpublishing.co.uk
http://www.choclitpublishing.co.uk/Submissions/submissions.html
More information here.