Unlikely to be heading for the boat since R118 was doing that plus they had already declared they were refuelling at Blacksod before comtinuing on any tasking.
If they had no NVD it is more likely they were using a legacy profile from S61 days to get to Blacksod - if this meant using Blackrock as a visual marker to confirm they were clear of any other terrain then it sort of makes sense but still doesn't explain how they came to hit the rock.