NonPCPlod - I think your question has been answered - unless the CG use a SAR helo in a completely different manner to how we used to use ours, the radar would stay on throughout the whole procedure, up to and including any transit below weather to the refuel site.
A simple FMS faff might explain how they ended up initially going towards Blackrock instead of Blacksod but once in the area with all the mapping it should have been blindingly obvious that the terrain was nothing like what they should have been expecting, from even the most cursory glance at a map or a LS directory - big rock in the middle of the sea vs LS at the end of a narrow inlet.
I would emphasise that this happened at 01:30 ish, a poor time physiologically to be flying anyway even if you have been rostered to do so. But, when you have been dragged out of your warm bed in the middle of the night, it can be doubly disorientating and make normal mental processes much more demanding.