LN-KGL, I would have thought a seasoned traveller like yourself would ensure you caught a flight that didn't arrive just behind our 1 x A380 a day!
I accept there can be delays at Border Control at certain times but then it means less wait for bags if you have them. And of course MAN does not control the staffing for Border / Immigration checks. All they can do is plead for extra staff or sensible rostering.
Out of interest, how much time would you allow for a scheduled meeting in London when landing at LHR or LGW?