According to my MPs newsletter, the date has been delayed -
"After asking Ministers, I was pleased to hear Royal Mail has seen the sense of giving a longer grace period and has delayed its proposed ban on non-barcoded stamps until next Summer. Previously, the new barcoded stamps would have been the only type of postage stamp allowed after January 31st 2023, with letters using old stamps being returned to the sorting office for collection after incurring a £3.50 fine."
First time I have seen any mention of a 'fine' though