There are hundreds of different websites that offer movies and TV shows but you cannot always be sure that what you're watching is legal.
The Industry Trust is an industry body set up to protect the media industry from copyright infringement.
If you are struggling to find the movie or TV programme you want to watch online then you can search for it directly using a content search engine like FindAnyFilm.com, which lists the cheapest places to watch films and TV shows online legally.
http://www.industrytrust.co.uk/
http://www.findanyfilm.com/
Where to Watch Film and TV from Legitimate Sources
http://www.FindAnyFilm.com
http://www.thecontentmap.com/film-tv/
http://www.bva.org.uk/media/19364/BVA%20video%20map%20November%202013.jpg
Where to Report Piracy
http://www.fact-uk.org.uk/report-it/
https://crimestoppers-uk.org/give-information/give-information-online/
http://www.cityoflondon.police.uk/advice-and-support/fraud-and-economic-crime/pipcu/Pages/Make-a-referral.aspx
Copyright Information
http://www.ipo.gov.uk/types/copy.htm
https://www.cla.co.uk/copyright_information/copyright_information/
http://www.copyrightandschools.org/#
How to Show Films Legally
http://www.filmbank.co.uk/
http://www.themplc.co.uk/
http://www.bffs.org.uk/
http://www.copyrightandschools.org/#
Cinema / Exhibitor Information
http://www.cinemauk.org.uk/
http://www.guardian.co.uk/film/series/at-the-british-box-office
Distributor Information
http://www.launchingfilms.com/ 
Video Sales Information
http://www.officialcharts.com/video-charts/
http://www.bva.org.uk/market-information
Lobbying Information
http://www.allianceagainstiptheft.co.uk/
http://www.creativecoalitioncampaign.org.uk/
Music
http://www.bpi.co.uk/
http://www.prsformusic.com
http://www.pro-music.org/
http://www.ukmusic.org/
http://www.ppluk.com/
http://www.ifpi.org/
Other Creative Industries
Games http://www.ukie.org.uk/
Publishers http://www.publishers.org.uk/
Football http://www.premierleague.com/
Fashion http://www.fdpa.co.uk/
Physical Piracy and Counterfeiting
FACT http://www.fact-uk.org.uk/
Crimestoppers http://www.crimestoppers-uk.org/
Brand-i legal directory https://www.brand-i.org/
Glossary of Terms
http://www.bva.org.uk/glossary
http://www.thecontentmap.com/jargon-busting/
http://www.fact-uk.org.uk/glossary-of-terms/
Facts and Figures
BFI research http://www.bfi.org.uk/education-research/film-industry-statistics-research/statistical-yearbook
Skillset http://www.creativeskillset.org/research/
DCMS https://www.gov.uk/government/organisations/department-for-culture-media-sport/series/research
Alliance for IP http://www.allianceagainstiptheft.co.uk/importance_of_ip_theft.html
Other Countries outside UK
Irish Trust http://www.lovemovies.ie/ and http://www.youmakethemovies.ie/
MPAA http://www.mpaa.org/
Australian Trust http://www.ipawareness.com.au/
South African FACT http://www.piracysucks.co.za/
Finding Right’s Holders of Films
BBFC http://www.bbfc.co.uk/
Filmbank http://www.filmbank.co.uk/
MPLC http://www.mplc.org/index/worldwide
BVA http://www.bva.org.uk/
Teachers and Students
Film Nation http://www.filmnation.org.uk/
Copyright and Schools http://www.copyrightandschools.org/#
Childnet http://www.childnet.com/resources/downloading/home/
The Film Space http://www.thefilmspace.org/
Working in Film and TV
Creative Skillset  http://www.creativeskillset.org/
My First Job in Film http://www.myfirstjobinfilm.co.uk/index.html
Filmcrewpro http://www.filmandtvpro.com/uk/?gclid=CJLPjs7e3rYCFerHtAod320ACw
Production Base http://www.productionbase.co.uk/
Freelance Video Collective http://www.freelancevideocollective.com
Film and TV around the UK
Creative England http://www.creativeengland.co.uk/
Film Agency for Wales http://www.filmagencywales.com/
Creative Scotland http://www.creativescotland.com/
Northern Ireland Screen http://www.northernirelandscreen.co.uk/
Film Certification
BBFC http://www.bbfc.co.uk/
Guilds and Trade Associations
Bectu http://www.bectu.org.uk/home
Equity http://www.equity.org.uk/home/
Directors UK http://www.directors.uk.com/
UK Screen http://www.ukscreenassociation.co.uk/
Making films
BAFTA Guru http://guru.bafta.org/
Creative Skillset http://www.craftandtech.org/
Bectu http://www.creativetoolkit.org.uk/home
Into Film https://www.youtube.com/playlist?list=PLE293992380B2B5D8
Shooting People https://shootingpeople.org/home
The British Film Institute offers classic and contemporary global cinema and documentaries, including free films.
http://player.bfi.org.uk/
Viewster offers a wide range of free series and films from around the world.
http://www.viewster.com/
BBC iPlayer
Channel 4's On Demand service
http://www.channel4.com/
ITV Player
Channel 5's Demand 5 service
IndustryTrust
https://www.facebook.com/IndustryTrust
Screenthing
https://www.facebook.com/Screenthing