Yes, but not in the bistro. We ate in the main house dining room.
We had the excellent value lunch menu which is £19 for two courses and £23 for three.
I had smoked salmon with poached egg and asparagus, roast lamb with cabbage and fennel potatoes and creme brulee with shortbread. It was all delicious with excellent service and we were sat at the table in the window which has a beautiful view, (see photo below).
All this and you can feel that you are helping the National Trust!