It could be a block in the bulkead
On two occasions my 159 mysteriously collected water in the driver footwell.
It was traced to a blocked bulkhead drain that was gunged up.
Really odd. I thought it was coming in through the door and I was going crazy trying to find the source.
The second time it happened I determined to solve the problem myself even though I didn't know what I was looking for. You have to remove the wipers and the plastic cover at the bulkhead end of the engine compartment. The driver side drain is substantially smaller than that on the passenger side...so this could well be a right hand drive issue only, perhaps as a combination of the wipers being reversed etc.
Anyway, happy to report no water ingress since addressing it in June this year.