photos, found where water is coming in
 

Started using water hose to find leak, nothing happened when checking sunroof,
moved to windshield, pulled rubber strip out of plastic frame and after a letting a slow stream fall behind windshield trim I saw some drops.

Gonna check windshield seal, now to try to get behind that plastic...

See where the drops are on the mat:
http://i221.photobucket.com/albums/d...SideLeak_2.jpg

Appears to be dripping off the fan motor:
http://i221.photobucket.com/albums/d...SideLeak_3.jpg

http://i221.photobucket.com/albums/d...SideLeak_4.jpg

Mine is leaking in a similar place, so I hope you figure it out!

Got the plenum off, found water travel path
 

Okay, I got the plenum off, I cracked it some more though... :o

So I saw this lower bolt was loose on the fresh air intake and water was around it:
http://i221.photobucket.com/albums/d...numRemoval.jpg

http://i221.photobucket.com/albums/d...irLoseBolt.jpg

Now I can see that water is in the blower motor area!
I thought there would be a cabin air filter here.... Is there not supposed to be one?

http://i221.photobucket.com/albums/d...hAirIntake.jpg

http://i221.photobucket.com/albums/d...irIntake_1.jpg

http://i221.photobucket.com/albums/d...irIntake_2.jpg

the fix
 

Okay, so I am thinking since the water is dripping down behind the plenum, where the air intake is, I am going to put a piece of plastic in place to help divert the water seeping behind the molding between the windshield and plenum.
It appears the water was seeping in where the air intake (plastic part) was sealed to the metal plenum area AND also was running down the plastic plenum and dripping down into the blower fan. The insulation between the firewall and blower motor was soaked on my D2.

I caulked the area around the intake for the HVAC and you can see the white caulk in the photos below in hopes this would keep water from coming in the cabin.

Source of plastic for me was an old piece of vinyl:
http://i221.photobucket.com/albums/d...takeMod_01.jpg

Cut about 9 inches long and now bending to put in place:
http://i221.photobucket.com/albums/d...takeMod_02.jpg

Following Savannah Buzz's tip for additional filter(https://landroverforums.com/forum/di.../#post316128):
http://i221.photobucket.com/albums/d...akeMod_101.jpg

Yes, there is water from the testing to make sure it doesn't leak:
http://i221.photobucket.com/albums/d...akeMod_201.jpg

Testing the filter fit:
http://i221.photobucket.com/albums/d...akeMod_102.jpg

One more photo with the plastic / vinyl diverter and filter:
http://i221.photobucket.com/albums/d...akeMod_202.jpg

Now to get the 'pollen filter' or cabin filter installed, Get the carpet dry, and get it all back together.

I'll report back if it leaks.

^nice work, I too am suffering from a similar situation. Please report on how it works out.

Looks like you are headed in the right direction.

If the heater core was leaking, there would be a distintive antifreeze smell inside. I had that happen to an old Volvo I had when I was in college in colorado.

I discovered water on my floor board the other day. Same spot. Truck was parked at the top of my driveway. Ldt us know how the fix works.