Just to clarify - the Sea King radar was used for over-water letdowns when IMC, day or night, with strict procedures about overflying radar contacts.
Night over-water letdowns using NVG(NVD/NVIS) were for VMC conditions but often backed up with a radar service from the rearcrew. Additionally in later years the FLIR turret could be used to enhance SA for letdowns, but the rearcrew were the only ones who could see that.
Out of interest, the Sea King radar was of a far better resolution than modern weather radars, had a much bigger screen with higher levels of processing and a dedicated radar operator - not a co-pilot who also has to perform PM duties as well.