You can watch Married at First Sight UK (MAFS UK) on E4, where new episodes air four nights a week from Sunday to Wednesday at 9pm BST (Wednesday shows move to 8pm). After airing, episodes are available to stream for free on the Channel 4 streaming service (Channel4.com), requiring a TV license and a UK postcode. If you want to watch without ads and get early access, you can subscribe to Channel 4 Plus for a monthly fee. For viewers outside the UK, using a VPN to connect to a UK server allows access to Channel 4's stream as the show is geo-blocked outside the UK. Additionally, in Australia, MAFS UK season 10 is available on the 9Now streaming service, typically with a slight delay after the UK broadcast. In other countries like the US and Canada, there are no official streaming options as of now, but a VPN can be used to watch via Channel 4 from abroad. For historical seasons or if you are in the US, Lifetime has aired some recent seasons of MAFS UK, although not all are easily available. Summary:

Location| How to Watch MAFS UK
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UK| E4 Channel (9pm BST Sun-Wed), Stream on Channel4.com free with TV license; Channel 4 Plus for ad-free and early access
Outside UK| Use VPN to access Channel4.com stream
Australia| 9Now streaming service (slightly delayed)
US & Canada| No official broadcast; some seasons on Lifetime (US); VPN for Channel 4 possible

This gives a full overview of where and how you can watch MAFS UK in 2025 depending on your location.