Well if I were you I would get to the airport 2 hours before.
At that time on top of the scheduled european and charter flights there are many flights leaving to the US (AA, BA, DL etc) together with EK and EY flights, which often create extremely long queues.
On top of that, it's rare to see all the desks and screening machines at work so it can get boring....just telling you from my experience.
Remember even if BA says you can take a wheelie bag + a hand bag, the secuirity people will object to that, so make sure that you can fit your 2nd bag inside the first, after security nobody will bother you anymore. Again, I am telling you because I know a couple of people in particular who are so petty I wonder why they are working there when they should be giving speeding fines instead!!
Having said that, you might be lucky and get through it quicker than I imagined, but I would be prepared if I were you!!
Happy flying!
FBW
