It looks like I have a leak from somewhere but a search on here and online just throws up L322 sunroof drains as the culprit.

The wet carpet doesn't seem to smell of anything like coolant and is clear by the looks of it but there seems to be a fair amount of liquid present. The top of the mat is bone dry and we've hardly had anyone in the passenger seat to cause the issue.

Any ideas where I should focus my attention tomorrow?

IIRC windscreen seals can fail and let water in, especially if you have had a replacement screen that might not be properly seated. I’m sure someone will come along soon and correct me on this. 2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW

I did have a look at the windscreen which is branded Range Rover so automatically assumed it was the original, but it may not be the case. The damp feels like it is from the edge of the A-pillar and down to the whole of the footwell.

Intention is to dry it out best I can then get some water detection tape and stick it around the trim in that area to try and narrow it down. I think a trip to the dealers is inevitable either way..

Thanks for the response, much appreciated.