Air-box Repair

The collecting tray under the vents has a seal between the front edge and the housing bulge (later type).  If there's rust inside that area (usually visible from the front luggage compartment), the water can get down between the seal and the housing, and drips onto the tunnel.

 

The air box needs to be removed, and then the tray - under the hood there are obvious spot welds around the base of the housing - these hold the collecting tray.  You could drill the spots (the metal just next to them really) and release the tray for repair.  The housing bulge can also be mended from inside if you are still flexible and can bend enough!

When I repaired the bulge, I cut a section out with a mechanical hacksaw blade, repaired it, then welded it with some spots of weld to bridge the saw cut and filled the rest with bondo.  Fiddly, but I guess you could get someone to do a few spots of weld without too much cost, or epoxy glues would do as good a job I guess.

 

I like the idea of the repair with the tray out, as that has a lip to stop leaves getting into the air-box, and mine on the Fastback needed a lot of fiddly work to get it mended in place.  However if the bulge needs a lot of repair, it may be easier to cut the section out.