This is a very useful thread. I wondered, a few months ago, whether the front door handles could be swapped around. I was interested, at the time, about whether you could fit the mechanics of the passenger side door handle into a drivers' side door handle. My drivers' side handle did the usual thing and stopped being pulled back into the door when the door was opened, and the passenger side door handle is freely available.
It looked like I may not have been able to get a new drivers' side handle from LR as they were listed as NLA and I wanted to keep the patina on the handles all the same, so I started looking to see whether by removing the spring mechanism in the back of the handle I could fit a new mechanism from the passenger side door.
However, I never did find out because [a] I ended up getting a complete new handle, keyed for my car, from Classic LR Jaguar, and [b] unfortunately no-one seemed to have tried it ! I really needed some spare handles to strip and rebuild but I wasn't going to buy a couple just to mess about with. In retrospect maybe I should have done.