Anyone see something wrong with this news headline?
It’s in the sub-headline.
You do not “lay” on a mattress; you lie on a mattress. You do not lay down; you lie down. “Lay down” is used as a verb requiring an object, e.g. “laying down a barrage” or even “laying down a carpet” — although to the ultra-picky, one just “lays a carpet” (the “down” is understood).
Chickens lay eggs, builders lay bricks (bricklayers), decorators lay carpets (carpetlayers, which has fallen out of use, and “carpet layers” has come into vogue, although “carpet layers” strictly speaking means a number of carpets lying (not laying) on top of one another).
In sexual slang, men lay women — historically, when a man “laid a woman down” or “lay (past tense of the verb) down with a woman”, it was a euphemism for having sex, hence “getting laid”.
If you get confused about all this, just remember: Hens lay eggs. It’s a transitive verb, requiring an object.
The key word is “lie”. Any time you use the word as an expression of becoming recumbent, it’s “lie”: lie down, lie on a bed and so on. The only time one would say “lay on a bed” is when it happened in the past, e.g. “She lay asleep on the bed last night, clutching her teddy bear.”
“She was laying on the bed” always begs the question: “Laying what? Eggs? Bricks?” The correct expression is: “She was lying on the bed.”
As to the correctness of having homeless Eastern Europeans lying [sic] on mattresses outside Park Lane shops: that is a topic for another time.