If you want to see one of the best descriptions (with animations) that I've ever seen on Silver Shadow Hydraulics, visit Marinus Rijker's
Silver Shadow Hydraulics Pages.
I have posted a file with many resources related to Rolls-Royce and Bentley parts, repair, restoration, and other resources
here. One of the things included in it is how to blank off the height control system should you so desire.
Just so you know, virtually all of the seal kits are nothing but a specific collection of standard sized O-rings in EPDM. I will soon have the last of the rings I need to put together several of the hydraulic seal kits, including the height control valve rebuild kit. The trick was getting the quad rings that seal around the shaft through the center of the valve.