At the Waldorf London in January, we were denied use of the lounge after checkout. We asked for late checkout, that was denied, then asked to use the lounge instead, that was denied also.
Upon checkin (at 3 P.M.) we were told no upgrades available. When we pushed it a bit, we were told an executive room would be available at 4. We took that, and had to ask to use the lounge until then, as they didn't automatically offer it.
We definitely got the impression that these run-arounds were not the result of poor training, but were hotel policy. In fact, we were specifically told that no lounge access after check-out was hotel policy.