Since I've had this 2001 P38 for 4 years the LCD display has been only partially visible, but the heater has worked fine and just required a bit of nous to get the right heat setting, I don't use the AC and it doesn't have a belt on it anyway but now the drivers side up down rocker switch is hard to press and seems stuck, passenger side still ok.
I have the old 1999 spare parts car and the panel was one of the working items when parked up, should this swap over with mine?

If the part numbers are the same, then they should. There were a lot of HEVAC revisions in the P38 production years, and some of the older units aren't compatible with the wiring on the later vehicles (AC compressor wiring changed and is the big one that might throw the book symbol - but if you don't use it then probably would be fine).

Alternatively - if it's just the pixels on the display going, then I do a replacement for the ribbon cable which is available on my website: p38webshop.co.uk It is a DIYable fix, and before committing to anything you can download fitting instructions on the 'Technical Information' page of the website too, so you know what you're in for!

+1 Marty is the guy for this.

+1 got one of his zebra connectors for mine as the screen went fubar. Also found that the buttons on the unit were all stuck up with some liquid or other causing them to stick in. All cleaned up with electrical contact spray and lubed with silicone grease now good as new.

JFC102550 or it's none heated seat version covers all previous Hevac units. Although you may have to change and move the ambient temp sensor for the newer one on very early cars. Not sure about that. It will not blowup any more than previous versions did by feeding the Aircon compressor. It is if you so desire a quite easy wiring change to incorporate and use relay 3 for this purpose. I don't think the harness Land rover supplied as a mod to use relay 3 is still available. Maybe not, but who would pay their bloody daft prices anyway.