P38’ers - I need some ideas about a water leak under the carpet on the drivers side!

The leak is more towards the door side and spans the footwell from a few inches in front of the BECM to the accelerator pedal. It is completely dry next to the centre tunnel and also completely dry at top edge if carpet against the bulkhead all the way across, so only about 1/2 the carpet is wet.

• sunroof drain is clear
• air con drains clear and no leak from matrix - centre tunnel and that side of carpet is dry, and it tastes like rainwater rather than coolant
• no leak on headlining (completely dry under headlining) or pillars at all
• it’s not the windscreen as that is less than 6 months old and top edge of carpet against bulkhead is dry
• I fixed up and sealed tears on the door foam/water deflector foam behind the door card already
• no water coming through the heater blower box anymore as I’ve fixed this leak by taking out the scuttle and pollen filter box etc. and sealing and repairing the area, sealing pollen filter covers erc as well as new inserts etc for scuttle area.
• grommets for bonnet cable and bulkhad cables look ok but have siliconed those

I’m a bit stumped and can’t think where it could possibly be coming from - any ideas?