what is sacrosant about...them all being located on the seaside
In case anyone really does ponder this!
It's because generally people in difficulty in the water have a lower chance of survival if rescue is delayed than somebody stranded with the same illness/injury on land = base the helicopters as close to the sea as possible (standfast Wattisham/Leconfield!). As it happens, most of the biggest hills in this country happen to be very close to the sea as well, albeit not necessarily near the SAR helo bases, but that's a different argument...