Not read through the whole thread, but you can sign up on the royal mail site for alerts on routes into your depots that may be causing issues for you.
When they put this new system in our region and Oxford I think it was, there were delays over 6 weeks. We had postie's we'd known for years throwing the towel in at the front door because of the abuse they were getting off people in the area. Essentially the transition to the new system meant there was weeks or months worth of post in cages with new stuff stacking up on top, hence, huge backlogs.
I asked our regular during the worst of it whether they were having issues, it's me, I'm polite, anyone that knows me realises I'm soft 😂 The guy practically ran away like I was going to kill him.
Few weeks later before Christmas left a box of biscuit bar things out for him to take back the depot, he ended up knocking and "updating us" huge offload... they'd lost a massive number of staff, huge backlogs, whole thing was a shambles.
It returned to "a normal" some months later, but of late we've had delays again, 5-7 days maybe. Don't lose hope stuff may turn up, but it has been a while 😔
