If you have your boarding pass printed, or on your phone, you can proceed to connections, go through transit security, and that's it. BA is now using the lounge in the non Schengen area. So you should be fine without entering the Schengen section.

There is not much in terms of restaurants or cafes, things to do in the non Schengen section, if you don't have lounge access and don't need a Schengen visa, for 3 hours I would pass through to the Schengen area.