It might sound a bit esoteric, but (as well as being middle-aged and married), I’m part of a pretty good social scene at the RSNB rowing club on the canal on the North side of Brussels. The rowers are about half-and-half Belgian and expat and there’s no shortage of English spoken. As well as rowing, the club has a table-tennis hall, outdoor basketball and tennis courts and a brand new sports hall for basket, tennis and badminton. There’s a beautiful old clubhouse with bar and meal service.
Annual fee is a maximum of €225 for access to all sports, single sports are less e.g. rowing is €175. There is a social membership for just €30/year. There’s also a learn-to-row course for €30.
If you would like to know more, contact me, firstname.lastname@example.org