"We must catch up sometime"
What it really means
Phrases like "We must do this again", "You should come round sometime" or "Let's get coffee at some point" are often friendly noises, not firm invitations. A real invitation comes with a date: "Are you free Saturday?" Don't be hurt if a vague plan never happens — and don't turn up based on one.
Context, tips & common mistakes
'You should come round sometime!', 'we must do coffee', 'pop in whenever you're passing' — these express goodwill, not plans, and treating them as bookable is the classic newcomer misstep (never literally 'pop in whenever': unannounced visiting has its own taboo). A real British invitation carries specifics: a date, a time, a place, or the machinery to fix one ('are you free Saturday?').
The conversion test works reliably: answer warmth with a concrete proposal — 'I'd love to! How's next week?' — and watch. Engagement with the specifics means it was real; a softer vaguer reply ('yeah, definitely, sometime!') means it was ambience, and you let it go with no hard feelings. Learn to issue your own vague warmth too; it is not dishonesty but social temperature-keeping, the pleasant hum of goodwill between people who may or may not ever have that coffee.