Yes, XX (2017) is free to watch on Plex in the UK with no subscription required.

Where can I watch XX in the UK?

XX (2017) is available to stream on Prime Essentials, Amazon Prime Video, Plex in the UK.

Yes, XX (2017) is currently available to stream on Plex UK.

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XX (2017)

RHorror· 1h 20m· ★ 4.6

This all-female horror anthology features four dark tales from four fiercely talented women.

Is XX free to watch?: Yes, XX is free to watch on Plex in the UK with no subscription required.
Where can I watch XX in the UK?: XX is available to stream on Prime Essentials, Amazon Prime Video, Plex in the UK.
Is XX on Plex UK?: Yes, XX is currently available to stream on Plex UK.