Playing Sonos through bluetooth mirror in bathroom

Not easily. If you have one of the three products with line-out or headphones, you could add on a Bluetooth sender and use that to bridge it over. But it's not gonna be easy, it's gonna probably be flaky, and it will only play whatever the source Sonos device plays - mirror will only play the exact same stream as whatever Sonos device is feeding the Bluetooth sender.

Thank you for taking the time to reply.
Would you happen to know whether there are any alternatives, like a Sonos speaker that I could put into the bathroom? Failing that, I'll just turn the volume up in the bedroom and leave the door open!

Hi. The Play:1 is humidity resistant and is marketed in some countries as suitable for bathrooms, but UK electrical regulations don't allow plug sockets in bathrooms.

The usual Sonos solution has been to have a Connect:Amp located outside the bathroom with wires running to ceiling speakers. I think that may be more hassle than you will think is worth it!

Thanks John
Yep, it does sound a bit more hassle than it's worth.

Appreciate your taking the time to help me

A further thought. Why do you need Sonos for this? Why not just Bluetooth music from your phone?

Doah, that is a very good point (told you I'm not technical lol)
Thank you!