Note: Resources for Writers UK does not endorse any of the following services. Getting a professional critique can be a fantastic experience - just make sure you do some good research (online, talk to other writers, etc.) before you leap in. (This is definitely not a comprehensive list, either - do let us know if you feel there's anything missing!)
Adventures in fiction - offer full manuscript, short story, submission package (cover letter, synopsis, first 3 chapters) and picture book appraisal
Cornerstones Literary Consultancy - offer plotting help, mini-reports, general reports and in-depth reports on full manuscripts, non-fiction proposal reports and consultancy reports (full manuscript report, plus 1.5 hour meeting with the person who wrote it)
The Literary Consultancy - novels, short stories, poetry
Writing Literary Consultants - full novel critique, copy-editing services
Clare Wingfield - full novel critique, non-fiction critique
Oxford Writers - full novel critique, marketing assessment and help
The Writing Coach - manuscript appraisal, coaching and mentoring