Is this in a rental? Describe the network there for us. Does the router have an obvious make/model? Did you need a password to connect your phone to the WiFi or is there an open guest WiFi?

Have you tried wiring the Play:1 to the router? That’s assuming you can locate an Ethernet cable...

It’s a holiday home, with 4G wifi.i It’s an Orange Huawei Router with a password.

i do not have an Ethernet cable 

You state “I can get both to see Sonos Wifi”. To my knowledge there is not such thing as "Sonos wifi". What do you mean exactly?

Normally connecting to a new network would not be much work, though the absence of an input for wifi credentials on Sonos devices makes it a bit harder than on, say, your printer. An ethernet cable would make it possible to connect the Play:1 to the router and then put in the wifi credentials of the router. You could buy an ethernet cable and try this.

If I follow the instruction in the App for when there is a new wifi, it asks me to connect to wifi on the iPad/iPhone, and to the network called “Sonos”. I get that far, then it cuts out with a note -”no internet connection."

The phone may complain about ‘no internet connection’. This is normal, as it’s temporarily connecting to the ‘SONOS’ ad-hoc WiFi from the speaker.

Ah. So it might work? 
 

off to try...

Ah, right the Sonos wifi is makes it possible to put in the credentials of the real wifi. The Play:1 works different from my One’s. Sorry if I caused any confusion.

Sonos themselves have fixed it