As a regular long haul passenger I can confirm that the opinion of regular passengers is that the cabin service is usually rushed.
That is particularly noticeable on flights departing Heathrow. A fellow passenger commented he had flown up from Nice that day and noticed 2 of our cabin staff were passengers (in uniform-hence he noticed them) on the same flight as himself that arrived more than 5 hours before the departure time of our flight. He thought they might be tired and in need of rest and that could be the reason for the rushed service on an 11 hour afternoon flight.
I would like to add that most of the BA cabin staff are the best in the business, it is a great pity not all of them are in this category, that is a management issue.
On other airlines we always see the equivilant of a cabin service director/manager visible in all cabins usually helping out with the service.
My last flight was with another carrier and the cabin manager was serving meals in the economy cabin and then spent some time walking around afterwards to see if anyone needed anything or just wanted to chat. The service was efficiently managed and not rushed.