At LHR the night jet ban is from 2330 local. Meaning no departures. However BA and BMI have a quota that allows them to depart a set number of aircraft each year. The BAA also I believe has a quota to allow other airlines to depart after this time.
When there have been bad delays during the day, ie bad wx or loss of runway then the night jet ban seems to be ignored.
In the morning some of the Far Eastern flights can arrive between 0530 and 0600 local, then after 0600 local its free for all.
There are some taxi and engine running restrictions on the south side of the airfield that affect Terminal 4 operations, however these are just to keep noise down for the Hilton hotel???
I would expect that Terminal 5 will have lots of draconian night noise restrictions making ATC harder than it already is.
Hope this helps and if I have made any mistakes feel free to correct.