There is a particular kind of London plan that should be easy and somehow is not. A film opens on Friday. You want to see it. You message the people you normally go out with. One is away, one has dinner, one has a child to put to bed, one can do next Thursday but you cannot.
Nobody has done anything wrong. The problem is simply that adult calendars stop overlapping as often as they used to.
The problem is coordination, not friendship
It is easy to misread this as a social problem. Often it is just a scheduling problem. Your existing friendships may be completely healthy while spontaneous plans become harder because jobs, relationships, families and travel all compete for the same evenings.
That matters because the usual solutions are poor. You can wait until everybody is free, which can mean missing the theatrical run. You can go alone, which is often excellent. Or, on the occasions when you actually want company, you can try to manufacture a whole new social plan around the film.
Start with the plan that already exists
Costar was built around a different order of operations. You do not browse strangers and then negotiate what to do together. You start with the exact cinema screening you would genuinely attend anyway.
If another compatible adult independently chooses that same screening, both of you can decide privately whether you would like to go together. The film is not an excuse for the meeting. It is the reason both people were going out in the first place.
Why this feels less forced
A shared screening gives the evening shape. There is a public place to meet, a fixed start time and an obvious subject to talk about afterwards. If there is no chemistry, you still saw the film you wanted to see. If there is, the evening can continue naturally.
That is the whole point: create more opportunities for real life without requiring your existing friends to have exactly the same free evening as you.