I believe that the S61s in Ireland (which had the SN 500 series autopilot like the SK 3A) were allowed, in extremis, to use the trans down SAR modes to runway which would get you to 40' fully coupled.
We used the LN450 to transition down running into Sumburgh @ 40ft when the 40 Mile an hour fog was about, using the localiser as a backup indication of the correct track to runway 27/09. It was a well established procedure by the time I arrived in 2004.
Si