Thanks Crab, appreciate your very helpful response, which confirms that SAR let downs can be in 0/0 conditions and 0.5nm offshore was your minimum. Presumably the S92 is even better equipped than the aircraft you were flying, so limits are not likely to be more restricting. So it certainly seems for this SAR crew, a task that requires a let down with say a 200ft cloudbase and 2000m vis, 2 miles offshore would be pretty straightforward stuff.
Given that, it seems extraordinary that approaching this refuelling stop at Blacksod was not a very straightforward task. Better weather, 5 miles of open sea south and 4 miles east, a sea level target with a big flashing light on top.
There's lots of finger pointing at a poor APBSS and this clearly had its inadequacies as the AAIU made Safety Recommendation 1 ref CHC route guides to essentially highlight obstacle risk and limitations of EGPWS. But then the APBSS (probably) included no transit heights which was therefore at the judgement of the flight crew. It was after all only described as a "route guidance". The associated notes and CVR briefings will add much needed clarity in due course.
Some have said it was negligent for there not to have been an IFR let down procedure for Blacksod. But whilst it would have been helpful, we come back to the point that these SAR crews are presumably spending much of their time making let downs that are far trickier - it is bread and butter to them - and they are highly skilled and trained to do it safely.
Ironically I'm sure it would have been far safer if this APBSS approach had never existed and the crew had had to make their own approach. It's existence probably lulled them into assuming it was a clear VFR route in so a standard 200ft transit was ok. Still doesn't quite add up with why the captain flew over what she said was a "small little island... that's BLMO (sic) itself". Odd thing to do at 200ft at night in poor vis. Maybe she thought BLKMO was more like 28ft than 282ft.