Ladybugs congregation in our bathroom

We live on the 3rd floor in a tenement, the bathroom faces south, the window is nearly always tilted, there are quite a few plants there.

I have often noticed ladybirds in the bathroom over the last couple of years, but there are now 5 huddles together for 3 days, and another few visiting (Monday evening there were 9 in all).

It's very sweet and we feel deeply honoured but it's kind of weird (none of the neighbours had more than one visiting).