There was one mentioned here that overnighted in Paris recently following a very late flight from LHR. I wonder if these days as BA isn't so short of aircraft they're happier to send a flight down and do a "semi planned" night stop and at least get one lot of passengers to their destination on the right day! I do doubt that Finnair would do that though since their aircraft would likely be needed back at base in the morning for a flight

As a random aside I think Finnair do rotate aircraft and presumably some crew in on their AY coded HEL-LHR-HEL nightstopper. But as they've got multiple aircraft based here then it makes sense that some would need to position in