I'm fortunate to have free lunches at work and, as it's a college, we have a staff / student restaurant.  Generally, I will eat my main meal of the day at work (took some getting used to, as I've always taken a packed sandwich lunch before), and then go for a cup of tea or coffee up in the Common Room.  If I'm seriously busy, I will skip that. 

When the restaurant is closed for a couple of weeks three times a year, we can get "take-out" from a local baguette shop (again, free to a certain £level) and I'll generally eat that at my desk, sometimes with a colleague, or on my own.

Sometimes I really miss bringing in the packed lunch when I would just shut my door (my own office) and just read a book.  But hey!  It's free and saves me money - I am not going to pass on it!