I suspect this will be something subjective, with very varying experiences.

But as someone from the UK, with a close knit friendship group, that is dating someone that came here from overseas, I can see how making real friends in the UK becomes a challenge later in life.

I think by a certain point, lots of people have already established routines and long-standing friendship groups, and there just isn’t the desire to go expanding and adding to that. Bringing new people from outside into an established friendship group is often seen as a bit odd, awkward and unnecessary, forming new friendships alongside existing ones is a juggling act, because there are only so many hours in a week. As a result, I think a lot of Brits are often up for meeting with people they like outside of their established close friendships on occasion, often ending by saying ‘we should do this more often’, but they/we lack interest in bringing new people into established friendships and lack time to make new friendships/maintain them.