Rainwater ingress - where from?

Hello advice needed please. My Gen 3 2001 Jimny has sprung a leak, rainwater is trickling down the inside of car on drivers side, emerging from under the cubby hole by the rear door and puddling in the tool well. This rainwater isn’t being forced in when driving, car is stationery, so I’m assuming a seal has gone somewhere local to the puddle? I can’t see anything obvious. Roof lining above is dry. Externally the roof bar fixing onto the roof has a bit of play, is there a fixing point that might allow water in? The side rear window is well fitted and all door seals are intact. Are there any gutters or drains that may have blocked? Any thoughts please?

Take out the trim panel 
Could be rusted through behind it. If it's not then put some talcum powder all over and the water ingress will show where it's travelled from 

Car was subject to extensive welding a year or two ago, be surprised if that was the root but will take panel off and talcum! I was just wondering if anyone know of any obvious bungs, stoppers or channels nearby that might need maintenance before I took the trim off. Thanks again for taking time to respond.

Rear light has a grommet behind 
but i doubt water would make it's way into the boot 

Thank you for the grommet info. I guess it’s off with the panel and out with the talcum powder….

I will second the talcum powder technique. Thought for a moment that I had wandered into a Land Rover forum tonight. Solihull really know how to build cars that leak and since purchasing a Jimmy. I no longer look for puddles in the footwells. Just be aware that newly welded seams and adjacent panels are not always 100% watertight but you are doing the right thing in seeking to sort the problem before more (expensive) damage ensues.

Stripped the interior, no sign of any holes, removed roof rail in case a hole from above - all sound. Removed drivers side rear body light cluster, no obvious leaks. Considering the bolts holding the rear door on may not have a washer / gasket, maybe creeping in through there? Some condensation on the crease of bodywork that forms the door opening drivers side, which is where the water came in. No real conclusion but not devastating.

Rear door bolts leak would not get inside i think.

Antenna on the roof?

Tried parking the car with a lean to sort out wich side it come from?
Remove door seals and cleaned?

If you wait long enough the black mold will tell where it comes from. That is how I found the leaky roof antenna on my daughters Swift