That's it! Exactly the same location. I will post a pic before I plug it. I never new Botang's hole was there, I thought it was further down closer to the middle.
What a nightmare!
The location is pure genius, it is positioned to trickle water down several wiring looms, drip onto relays and onto a group of earthing points on the chassis!
Thanks I will give those bolts a try. I was going to just use an aluminium bolt and washer filled with silicone, but those look better.
Thanks for your help
P.S. even though it rained all night, this morning no more water in the footwell, so hopefully Botang's hole is the only leakage point on mine.