I try to use the Tesco Express that opened nearby in the summer only for items that I cannot get in the local independents. There are one or two grey areas, though. All the Turkish and North African supermarkets sell garlic and courgettes; but Tesco's garlic and courgettes are rather good. The garlic cloves have purplish skins, are firm, and do not have bitter stalks at their centre. The courgettes are firm too: their flesh is not pulpy, and their skin is not acrid. Yesterday, for lunch, I simply sauteed them in olive oil as an accompaniment to scrambled eggs on toast.
Courgettes cut into batons retain their firmness for longer when cooked than do sliced ones. (The same phenomenon is true of carrots.) Despite the risk of overcooking, I usually prefer to slice them: the skin is less noticeable that way. Some people salt them first, to extract some of the water that they would otherwise disgorge in the pan and that would stew them; but I am not so disturbed by the odd soggy courgette that I am prepared to go to that effort. I put a layer of olive oil in a large saucepan, turn the heat to medium, throw in the courgettes, grind over salt and pepper, and cook, stirring almost constantly, until the pale flesh goes a darker green. I might add chopped garlic (probably also from Tesco).
Here is a recipe for spaghettini with courgettes.