The ferry used for the exterior shots was the King Seaways operated by DFDS between Newcastle and Amsterdam but with different livery added in post production.
The elderly ladies are traveling in honor of their friend Marge, one of the victims in the previous movie Murder on the Blackpool Express. Another friend from MotBE, Peggy, does not appear and is not mentioned. The actress playing Peggy, Una Stubbs, passed away before this was released so perhaps was ill or otherwise unavailable to reprise her role. Una Stubbs died in 2021. This was released in 2018,