Caffe Ritazza, Paddington Station

You're rushing for a train, caffeine-depleted, and suddenly there's actually something worth drinking. Caffe Ritazza sits in the station proper, and whilst it's easy to dismiss as transport-hub convenience food, they genuinely nail the Italian coffee thing. The espresso has proper body to it—none of that thin, burnt nonsense you get at most chains. It's the kind of spot where locals queue because they know the coffee's decent, not because there's nowhere else. Grab an espresso or a proper cappuccino, maybe a pastry if you're feeling it, and you've sorted yourself out better than a Costa would manage.