Earlier quoted context omitted.
My experience living in London was that most of my colleagues were perfectly content picking up a sandwich from the nearest EAT or Waitrose or whatever. Every day a tired, boring sandwich for lunch. I just couldn't understand it. Some stores were just aisle after aisle of sandwiches, I'd never seen anything like it.
Prepared, packaged food in Britain, especially London, is much better than most of Europe. In Germany or France, a sandwich from a supermarket isn't fresh, isn't good, and isn't interesting. In Britain, it's at least some of these things. In France or Germany, you can go to a bakery and buy a sandwich, but that's slower and dearer.
Having never been to M&S but having a vague awareness that they exist, I didn't know what to expect, other than to think that if I saw Qantas advertising a new menu "co-created with David Jones" I'd be rather suspicious. I've since been to a M&S and discovered their rather extensive food section which is rather better than the average Australian department store.
(Of course, BA, like all other European airlines I've experienced, is distinctly average at best, and having to pay for M&S prepacked sandwiches is definitely part of that.)