Can sonos work without a wifi router

Another way to answer the OP question:  Yes, you can use a non-Wifi router.

You will need to wire one Sonos device into the router.  No need for wifi.

If you have more than one device, the one that is plugged into a router will create a wireless network (just used by other Sonos devices).  

Of course, if you don't have ANY wifi network or access point on your network, you won't be able to use mobile devices like a phone or tablet as a controller.  You will have to use your computer to control the Sonos system -- or perhaps find one of the discontinued dedicated Sonos controllers.  

(There is one geeky techie workaround involving android devices and setting up a temp wifi network to configure it and then switching it over to sonosnet but that's going off the deep end.)

In short, though:

1) You need a router.
2) It does not have to be a wifi router
3) If you don't have a wifi access point somewhere on your network, you will be limited in how you can control the sonos (hard wired computer will be required).
You can add a mobile app controller without Internet connection like if you had friend come to location and want to add it to their phone. Friend would just need signal to be able to download on their phone or download to phone before get there if no cell service.

Hi, I'm no geek but I'm getting married in France in august and I'd like to set up a few sonos around the main house. The wifi isn't great, will this be a problem? If so, can I connect one of them direct to the laptop and if so, what cable will I need. Cheers, Matt

As you have a Play:5 the simplest solution for getting it to play is to connect laptop headphone socket to the P:5 line in. You have to set up Autoplay on the P:5 first, while it is still connected to a network. The 3.5mm to 3.5mm cable supplied with the P:5 is suitable for this.

Incidentally, do you mean that the wifi is dodgy (which would be relevant) or that the internet connection is dodgy (which wound not be relevant for local content)

There is also a possibility to use an Ethernet connection between laptop and a Sonos speaker that potentially (I think) allows you to play a Sonos music library across a group of speakers, using something called Auto-IP. But the grouping aspect is a bit technical and I have never tried this myself.