Tonight we have lost all but HD channels on the box
Have you checked that the aerial cable is plugged in properly, does the aerial itself look OK, is there an amplifier somewhere in the aerial cabling that has failed? If it is none of those things then try an automatic retune with the smart retune option on; if that fails then try again with the smart retune off.
Are they lost, or are you just being offered the “HDTV” group? If you go into the guide, select the “+OPTIONS” then “Change group”, then “TV” you may find they all reappear.