Not only did Edgar Wright shoot the flashback sequences featured in The World's End on 16mm celluloid, he shot the whole movie on film. It makes a difference, and more than just matching well to the other two shot-on-film installments of the Cornetto Trilogy.
My exhaustively comprehensive review of the Blu-ray is almost finished. Three years ago, I did the same for his ultra-stacked Scott Pilgrim vs. the World.