The seats also have no headrests, but they are cloth rather than leather (which I do prefer).
However, the seats in general were quite comfortable on my WAW-LHR flight.

Ultimately it is a downgrade in comparison to most of the BA short-haul fleet, however these aircraft are all over 20 years old, so I doubt Finnair have much reason to upgrade their cabins when they will probably be retired soon.

Wish BA were more transparent when changing flights to Finnair, as I didn't get any e-mail telling me about this flight either.

And also, make sure you're early at WAW for check-in (unless you're in CE or have BA status) if Online Check-in doesn't work (it doesn't work sometimes for WAW flights), as the queues are awfully long to get checked in!