DB - only the 3A Sea King has a TAS hold - the autopilot functions are pretty basic but the RNAV can fly the aircraft round the sky. There are the normal rad alt and bar alt holds with a manoeuvre facility but that is it.
There is no way, other than on the SAR transitions, to get the aircraft to fly any form of approach other than the TAS hold for an instrument approach.
For the SAR transitions to and from the hover, it is fully coupled and, if required, either the cyclic or collective programs can be manually flown.