I agree with a lot of the comments above and it is particularly embarrassing working for Customer Services when you have to deal with these problems on a daily basis (albeit in T2 which generally isn't as bad).
However on the subject of Immigation, I'd like to point out that the passport control staff are employed by Her Majesty's Government and not by Manchester Airport and therefore any issues with staffing are not the direct responsibility of the airport. We can advise them that they need to put extra staff on at certain times but whether they do or not is out of the airports hands.