We flew out of Manchester terminal 3 last week and it was as rubbish as expected. I'm sure terminal 3 was designed for about 10% of its current capacity.
Apparently it was quite a quiet time for security but we still were in the queue for around 45 minutes. Mainly due to idiots who didn't take everything out of their bag, so loads were getting the full bag search. (including my wife who decided to leave a metal tube of hand cream in her cabin bag).
I don't think it helped that our flight was delayed by 2 hours, so I'd lost the will to live by the time we finally boarded. Sitting in terminal 3 for 4 hours was not fun.
To be fair, the other 2 terminals aren't as bad, although I imagine security is just as long.