I've had a look unserneath for the mysterious slider but never found it.
I am replacing my left side mirror soon and have part on way via ebay hopefully- make sure you have the correct part as there are chromatic and non chromatic ones and ones with and without blindpost as well as shaped glass too. Someone has commented elsewhere that for the Range Rover L322 there are 12 different mirror part numbers listed depending on LH, RH, LHD, RHD, flat, convex, etc.
Anyway these links may help
First is from this site
http://www.xoutpost.com/submit-articl...=change+mirror
Also see this link to Range Rover net - I believe early 2002 L322 Range Rovers have same mirrors as the E53 X5 2000-04 . The only official reference I have seen online for changing one is in the attachment to the link below in the 2nd post. Click below and scroll.
http://www.rangerovers.net/forum/vie...=glass#p191836