You will need a Sonos product that has an aux input.   A Port, Amp, or Five.   You will need a preamp for the turntable.  Many turntables have preamps built in, but it does not look like the one your acquiring does.  The turntable that Sonos sells on their site, for example, does.

Thanks for the reply!

So, I’m looking at Turntable > Preamp > Port/Amp/Five > All speakers

Would the Port/Amp/Five give any benefits over each other? It looks like the Five does everything I’d need it to whilst also being a speaker

Get the Port if you want the cheapest option or connect to a 3rd party amp/receiver.  Get the Amp if you want to power some passive speakers.  Get the Five if you want the built in speaker.  No wrong answer, just depends on which option makes the most sense for your setup.

And to put a slightly finer point on it (sorry, Danny :)) there’s no difference between the line ins on the various Sonos products, beyond simple form factor. They all work exactly the same. 

That was implied in my answer! 

inferred, perhaps, not implied. :)

Thanks for your replies guys, really helpful. 
If I went with the Five, does the music have to be playing out the Five to then stream it to all other speakers? Can it simply be used as the aux connector between the preamp and the Sonos system without playing itself?

Yes - the ‘line in’ port to the speaker is effectively an ‘audio source’ (like Spotify or Amazon music is an audio source) - so you would just chose that source from the App ‘services’ list for playback on any Sonos room/speaker or group of rooms/speakers. Photo attached shows a Sonos group playing the line-in audio source from a Five (which is not part of the playing group).

So, the real answer is “no” to your question. The line in does not have to be playing on the Five in order to get it to stream to your other speakers. 

Perfect! Thanks very much for your help