Google began offering movies in 4K resolution in the US and Canada in December 2016. 4K UHD titles are now also rolling out on Google Play in the UK, with prices typically ranging from Ł10 to Ł14 pounds.
4K but not HDR
There is no official word from Google yet but as noted by John Archer on twitter a handful of 4K titles are now available in the UK. Some are available to rent whereas others are only available to buy.
The selection is fairly limited at the moment but we have discovered titles such as Spider-Man: Homecoming (Ł13.99), Concussion (Ł9.99), Captain Philips (Ł9.99), and Passengers (Ł13.99).
It should be emphasized that the movies are available in 4K resolution only. HDR, or High Dynamic Range, is not currently being offering in the UK despite being available in the US and Canada. HDR is often considered a bigger improvement as it expands the luminance range and color space.

To stream 4K movies from Google Play Movies you need a Chromecast Ultra or a supported Android TV device such as the Nvidia Shield. It is not currently supported via the Google Play app on Smart TVs and Roku devices.
The company recommends that in order to stream 4K titles, “you’ll need a consistent download speed of at least 15 megabits per second”.
It appears that Google is rolling out support ahead of an official announcement. We have browsed through other local stores but not discovered availability of 4K titles outside of the UK (and the US and Canada). Let us know if you find anything.
- Source: Google via John Archer