I finally realised from all the disparate bits of information that I need the Jessie img.
However, after installing, updating to the beta, adding the BT module and installing LMS, I am no further forward. The BT install appears to be successful (apart from some blurb about jivelite and pulseaudio ???). However the BT page never shows BT as installed – just repeatedly offers to install BT.
I am now doing reinstall number 8 of the whole system.
I only want the server stream feature – no speakers or direct audio.