Dunno if anyone else has tried this and I don't imagine for a moment that it's recommended procedure, but it does appear to work... Also don't know if it would work on anything other than the Disco II.
If you've got that situation where the air suspension won't maintain height correctly when running, and either goes low or high (one side or both) and the pump and air springs are OK, then you have height sensor problems. Here's something to try...
plug in your diagnostic gadget (or someone else's), put it into test mode for air suspension and us the air sus height function to manually set it to correct ride height as near as you can judge it (helps if it's on flat level ground!), then go into configuration and switch it from "air" to "coil" (or maybe "steel"). If your disngostic gadget is like mine it will have warnings about this, ignore 'em :)
switch off and disconnect diagnostic device.
You now have passive air springs, as the whole air system is turned off.
If you need to alter it again, switch it back to "air", whereupon it will likely tell you to test and calibrate the system, but you can still use test mode to adjust it and then switch back to "coil".
Ran around today like this, with no issues. It sagged a touch with weight in the boot but then it'd do that anyway with steel on it... if you were carrying a really heavy weight you could always adjust for it manually.
I don't regard this as a long-term solution, I have steel springs on order for it. But as a short-term get-you-moving type solution it looks pretty good.