hi there, one of the tricks I have used, especially on HMS Norfolk when I rebuilt her for access to the rudder posts is - on the flight deck - there is a circular landing spot painted on the deck - and I have cut through this and made it into a hatch - so it is camouflaged in with the white paint of the circle. It just gives enough room to give access to the rudder posts and linkage. It is a bit of a faff but I can managed to put an allen key in the hole and tighten up the grub screws on the linkages. The servo is in the main part of the superstructure, underneath the helicopter hanger along with the motors and so forth. Couple of pics - and you can see the circle on the flight deck. Also, have a look closely and you will see the rudder servo.
As an after thought (but I don't have a picture of the type 23's) I also use what is known as a closed linkage loop steering system. This helps eliminate failures.