Maybe check your online Sonos Profile and check it’s set to UK 

https://www.sonos.com/en-us/myaccount/user/profile

Thanks. It is UK but made no difference. 

I can only think that something is perhaps blocking access to the service on your local network - maybe try different DNS server(s) on your router. Maybe try the Google DNS public servers 8.8.8.8 & 8.8.4.4

Also check there is no security software running on your mobile, such as VPN client or Firewall.

I’m from the UK too and Alexa is working okay here - so my thoughts are it’s likely something ‘local’ to your own system/network-setup.

Thanks, but there was nothing changed at this end. It worked in the morning but when I returned in the evening it had gone and I can’t reinstall

Then it maybe best to submit a Sonos system diagnostic report from within the Sonos App, note it’s reference and then contact/chat with Sonos Support Staff via this LINK and see what the Staff can perhaps suggest to resolve the matter. 

And now it’s back! No idea why - I changed settings in the Alexa app and something must have done the trick. Mrs Nialli’s happy to have it working again - sh says Alexa’s the only thing in the house who listens to her!

ha ha  glad it’s working now, but how strange eh?... Anyhow Merry Christmas/Happy Holidays.