Years ago I started a thread called "What happened to the "Divi"". It was mangled by some unknown person who invaded the website, but part of it remains as "Re: What happened to the "Divi"". In it you'll see that my spelling of co-op was kworp.
Maybe that indicates a slightly different pronunciation of the word in our two families.
In the younger generation it is definitely gaining ground.
Th' sound to vanish from English language by 2066 because of multiculturalism, say linguists