Folks,
I have had an isue with my plus four in that there is little or no sound output from the front speakers. I had the factory look at it and they removed some padding in front of the speakers which had little or no effect so I have just lived with all the sound from behind!!
Now - the internet radio in Ireland is very patchy and DAB does not exist so I have decided to mount a Pioneer radio in the panel behind the seats(similat to the new lockable box) and connect it to the amplifier instead of the Musicstream unit. I did a "Dry run of the connections yesterday and - lo and behold -- the fade and balance adjustment of the radio unit produces perfect sound from all four speakers!!!! I just connected the pioneer head unit to the Kenwood 1804 unit as per its instructions so I dont know how the factory made a "Bags" of it!!
Anyway - I will complete the install when I get delivery of the aerial for the radio and will enjoy the full sound -- the Bluetooth connects now to the radio

so all functions of the musicstream are available and it has the benefit of providing a handsfree answer of phone calls should they come in!
RESULT!!!!