This franchise has failed. It cannot provide the PO services safely.
It should be terminated in its current form. Today.

The Post Office is being systematically and deliberately destroyed, and realistically the old purpose built office will not be reopened, nor any smaller shop converted. So we are stuck with franchises.

Sainsburys might be interested in providing limited services. They have the experience of dealing with larger sums of money and have more ground floor space.
WHSmiths could also run a one man sub post office on the ground floor - for parcels/registered post etc. With the upstairs space returned, and the bigger money elsewhere ,the shop would feel safer and lighter again.