The only other possibilities are either 4G or satellite broadband. There are no 'boosters' that will improve your speed I'm afraid.
@marcuspos wrote:
No immediate neighbours and no BT plans for any lines upgrades…
The try the USO option as mentioned, you may be able to get a faster connection without having to pay extra.
Its Openreach not BT Retail, that provide the network.
It says our property is not currently an eligible postcode…
Your postcode may be unique to you, if you are that remote. I assume mobile broadband is not an option?
Have entertained the idea of 4G mobile broadband, yes, but I have a large Sonos music system which, according to them, does not marry well with such broadband
No idea why it shouldn't.
If you say that, is it something I should be investigating further then? Why would they say it is not a good combo, stability of 4G perhaps?
How are you using your Sonos system, purely within your house or streaming from the internet?
If the former, method of internet connection is irrelevant, if the latter your 4G signal will be an improvement on your current broadband so no idea why Sonos say it won't work.
Both - use existing playlists from Apple Music and also listen to TalkSPORT etc via tinternet
Can't see what the problem would be other than possibly latency on a 4G connection. Ask Sonos to elaborate as to why they think it is a bad idea.