www.adzuna.co.uk
www.totaljobs.com
www.jobsite.co.uk
www.reed.co.uk
www.monster.co.uk
www.fish4.co.uk
www.indeed.co.uk
jobs.theguardian.com
jobseeker.direct.gov.uk
www.jobs.nhs.uk
www.tes.com/jobs (education)
www.greenjobs.co.uk (environmental jobs)
http://www.gorkanajobs.co.uk/ (journalist and PR jobs)
https://www.cwjobs.co.uk/ (IT)
https://www.technojobs.co.uk/ (IT)
More specialist sites are available at:
https://www.workable.com/best-specialist-sites-to-post-jobs
Here is a selection of useful sites if you are looking to move into the charity sector:
https://www.charitychoice.co.uk/charities
https://botw.org.uk/Society/Philanthropy/Organisations/Fundraising/Grants/
http://www.thehelpingfoundation.org/
https://en.wikipedia.org/wiki/List_of_charitable_foundations