Thank you for your responses. Take a look at the following - in 2010 a couple did exactly what I plan to do in the same vehicle. They only have praise for it. A completely trouble free run using air suspension. http://www.lilongwedown.com/LilongweDown/Trip_Log/Entries/2010/7/10_The_Range_Rover__a_eulogy.html
That's an L322. Sorry, thought we were talking P38. That L322 will have been less than ten years old at the time. Something to bear in mind. Beware the GM autobox. Jag v8 is the engine for reliability.