Further to my last Uber negative review...
eventually I made a connect! What I discovered is that if you have a BT SmartHub you will now doubt have the My BT app. The thermostat for some reason gets put into a default group in the app even without connecting. Remove the thermostat (shows as unknown_xxx) from the default group and it connects. Just the sort of thing Joe non IT person would discover with the non existent support I have had.