More about 2a. The Gospel Singing
Heaven is hearing Mahalia Jackson sing the gospel in Madison Square Garden. Hell appears to be sitting next to people who believe in God.
Hockney's dad was a good working class bloke but a Methodist, rather than a souless commie. He was also a rare pacifist during WWII and a conscientious objector.
Nonetheless, Hockney did not care much for religion.