"48 missiles but only 8 launchers?"
Irrespective of your question being "hypothetical / rhetorical", what launchers and what reload? The Type 45 has a VLS (Vertical Launch System) incorporating silos. 48 Sea Vipers in a VLS is a vast improvement on a twin launcher with 22 Sea Darts (Type 42 Batches 2 & 3) or 40 Sea Darts (Type 42 Batch 3).
The classic layer-defence system would have CAP taking out most of the shooters (air or surface) before they got within target acquisition / identification range anyway leaving the Type 45 to deal with any leakers with its hard kill and soft kill countermeasures.