You'll find plenty of public seating throughout the main terminal areas, near the departure gates, and on the northern walkway (near Gate 10 and the Eastern Airways lounge).
If you're looking for your own space away from the crowds, book into an airport lounge and enjoy peace, quiet and complimentary drinks and snacks for up to three hours before your flight. It costs less than you might think, too – find out more about airport lounges or book a lounge pass now.
For a completely different kind of relaxation, try the coin-operated massage chairs in the departure lounge (after security). They're great fun and it doesn't cost much to have your pre-travel stresses stretched and soothed away.