Gina it is the same principle as Bentley vrs. Seat.
Better transportation, better cuts of lamb, better packaging, lesser sell by dates, better refridgeration, better presentation. less additives.
I am not completely aware of the whole meat process, nor other foodstuffs come to that but the fact of the matter is M&S sell better quailty food than Morrisons, or whoever use the same lamb.
It is not snobbery, it is a fact.
I will bet my house that if you gave me a Pepsi Challenge (look it up if you are under 25 years old) I will tell you which lamb came from where.