Bongo Fury

Hi I have had an apparent "water" leak which appears on the offside cill seam 200mm behind the door close panel and drips in varying amounts after very short journeys. Due to the many posts regarding water leaks from the radiator cooling system I have had the system pressure tested and no leaks were detected and problems with the water pump have been discounted by the garage.
This leads me to suspect the "water" leak is from somewhere else but as there are no visible leaks only water dripping from the cill seam I am at a loss to know where it is coming from. The garage has suggested I collect a sample of the water so they can try and Analise its make up to determine its source.
Only thing I can think of now is aircon condensate but that usually appears under the centre of the front of the vehicle

Any help much appreciated

Rear aircon unit is right there, and does drip condensate - but do a good check of the pipework in that area too, just in case.

Thanks, after pressure testing the system (for an hour)and having the van on a hoist the mechanic were at a loss as to source of water leak so I have been driving van with air con off and no leak appeared and water level in expansion tank stayed at a constant level.
However on returning from a long weekend away on the West Coast climbing a steep hill there was a 'strange' noise I checked rear view mirror to see a puff of 'steam' so i pulled over immediately and stopped. All coolant from expansion tank and radiator had gone.
Filling the radiator and expansion tank after a cool down period showed a major leak so I got home on the back of an AA transporter. I shall get it transported to the garage that did the pressure test and get them to identify the leak more easily by poring water in and seeing were it comes out and hope I stopped in time to prevent any of the other issues that I have heard about and dread!