"Pride and Prejudice and Zombies" is the most serious zombie movie that I have actually enjoyed to date. It is still a SILLY movie, but the silliness is in the conception, not in the execution, which is ALMOST deadpan. Almost. I have gotten the impression that both of this movies natural constituencies dislike it; Jane Austen fans don't like zombies, and zombie fans are not very fond of Regency Romance. Dementia and I can't take zombies OR Regency Romance very seriously, but are familiar with both genres, and enjoyed this movie (except for the stupid "Gotcha" ending) a great deal.
"The Lady in the Van" was marketed as a comedy, at least in the United States (it is really a slice of life, and only occasionally funny); the story was better known in the UK, and probably more or less sold itself. The story is mostly true and more than a little bizarre. We didn't exactly dislike the movie, but we didn't enjoy it much either.