The A109 was selected (Actually confiscated) for the SAS for its speed and its main use may actually be as a bus for picking up personell in an emergency, this much I do know its not quiet and most of the civilian A109s here are long models, whcih still incidentally look nothing like an S-76.
H-60s are too long and heavy for Eithne, and very small for what you pay in TT terms, the Sea King types in the tender weren't just picked for their SAR capabilities, larger Helis are also better for us green wearing types.