Selling cold meat 7 days after sell by date

Hi,

I like buying items from checkers that are on their last day according to the sell by date as they get marked down and I can use them that day. It is up to me if I wish to wait longer before using them and I know the risks involved. On Saturday the 29th I picked up a few packets of marked down cold meats (with the 50% off stickers) and I intended to use them on sandwiches today ( Sunday the 30 ). The 1st packet I opened had a slimy film on the meat and I quickly checked the expiration date. I was shocked to see that the sell by date was the 22 nd of June. This was a week ago! How can they keep these on the shelves? I have taken photos of my till slip together with the products to show the sell by date and purchase date. Can someone contact me in this regard.

I tried the consumer care page on their website, but I received an error, so I am posting it here and hope someone replies.