I hope you send your complaints up the chain and they do something about it. I'm spending a week there (no choice) later this summer so I hope I can get the time of day from them. I'm paying for an Executive room (125 GBP) so I won't have to worry about an upgrade.
I'm really surprised about not allowing late check out. Isn't that mandatory for Diamonds? I've never had a problem with any Hilton, Starwood or Hyatt doing late check-out. And I'm only Hilton Gold!