Dont go off the info on the i bar, this will only tell you that the sound is being transmited in Dolby Digital. However it will not display the info 5.1 or 2.1, If your home cinema amp is conected and set up right. The amp will automaticaly decode 5.1 when transmitted.
Tip. Leave your amp in Dolby Pro-Logic II setting this will give you 5.1 sound all the time. And when the BBC HD transmit in Dolby Digital 5.1 your amp will decode this sound and return to Dolby pro- Logic II when the BBC return to Stereo or 2.1.