Earlier Bofors adoption changes the medium AA layer

What would change if Britain licensed the 40 mm Bofors before the war and used it instead of the pom-pom?

Britain would likely build its own multiple mounts and gain a longer-ranged medium AA layer, with the largest operational effect in the Mediterranean rather than every theater.

The Royal Navy would probably develop multi-gun Bofors mounts rather than simply copy every American mounting choice. Larger ammunition trays might follow, though their immediate appearance is less certain. Earlier Bofors adoption would extend the range of dense medium anti-aircraft fire and could matter especially in the Mediterranean. The pom-pom was still a capable weapon: it traded shorter range for a high rate of fire, so the two systems offered different advantages.