Looking to watch, rent or buy a film or view a television show, and you're not sure where the best place to go might be? This is where Justwatch comes into play. Simply pop in the name of the item that you're interested in, and it will see who has it available, and at what price. It search across resources such as Amazon, iPlayer, Google Play, Microsoft, Netflix and so on. They say of themselves "We are glad you're here! On JustWatch you can easily find out where to watch your favourite movies & TV series in the UK. JustWatch is easy and effective: Choose your favourite streaming providers and see what’s new on Netflix and other providers. Filter by genre and release year to find the perfect movie to stream tonight. Search for a specific movie or TV series to find out where to watch it legally online."
I tried it out for a few different films and tv programmes and it was ok. It didn't find the older stuff that interested me, but that's not a surprise. It did have some oddities - it had Strictly 2010 but no other years for example. However, it's worth a look if you want to find something in particular. You can also get an alerting service to tell you when there's been a price drop as well.