I'm afraid a Navy Sea King doing an ILS would be far from normal, given there aren't fitted for ILS (or VOR, or DME or ADF.....).
Crikey - presumably you do have some onboard navaid (GPS? TACAN?) to get down from VFR on-top? Or do you just avoid that situation?
WIWApongo we used to believe that the RN junglies could fly Seakings upside-down in a pint of Guinness - was our faith misplaced?