It's been the case here for a few years. I very rarely get post on a Monday, sometimes get mail for other addresses & have mail left on the drive or in the open porch, not through the letterbox in the front door.
When I went to the local sorting office to complain I was told to f*** off. There's no local telephone number. Long time Posties say the management don't care. Using Royal Mail complaints online produces zero response.
Being set up to fail for full sell off?
Amazon delivered next day with some bike parts on Sunday, Royal Mail is due 19-21 Sept delivery for an urgent tool ordered last Thursday - the supplier is under contract with Royal Mail & won't offer next day with DPD.