Of course, BA is not a premium airline. It may have premium classes and passengers, but whenever I've flown BA, whether in F, J or distress, economy passengers have far outnumbered F and J.

lhrworker makes a good point. OT I know, but I was delighted to find a McD by the gate when flying AA in F on an evening flight with no catering from ORD to LAX. I was the only pax with food.

About M&S, LTN has an M&S Food store outside Arrivals landside but not airside. They seem to do a heap of business.