A friend is working in a Waitrose in Brum, and says that shortages are getting worse. Partly to do with Covid; but that's a minor effect compared with Brexit.
I was also chatting to a cashier in Sainsburys a week or so back, who basically said the same (after telling me horror stories of angry customers pushing him out of the way when he was stocking shelves; and of people barging into the back of the stores, accusing them of hoarding all the food for themselves).
I've seen empty shelves on a regular basis in Sainsburys, Aldi, Lidl, and Waitrose when shopping recently.