In addition try to smell the damp carefully. This might indicate that its coolant from a failed heater or screenwash fluid from a leaking tube. Also clean the drain holes at the bottom of the doors with a wooden cocktail stick in case water is building up inside.

Then check any grommets in the floor plan are present and effective. We had a Corsa that was ex-BSM and the dual controls had been removed before we bought it but the holes hadn’t been sealed.

if it has a sunroof check any drain holes.

If that all fails use an indie to trace it.

Thanks for your suggestions. Does the plastic area below the windscreen have to be removed? There has been a leaf build up to the left and right of the scuttle but that is with the scuttle in place.

Tracing water ingress on cars is a very time consuming process. I would think the dealer would remove all the load area trims and rear seats and carpet for inspection. However, I’d start by checking the drains on the scuttle by the windscreen wipers before anything else.

Thanks for your suggestions. Does the plastic area below the windscreen have to be removed? There has been a leaf build up to the left and right of the scuttle but that is with the scuttle in place.

As has been said, tracing and stopping water leaks can be tricky, but meantime its fairly straightforward to reduce their consequences by removing floor and other drain plugs, so the drains actually. like, drain.

I was able to decimate the frog population in my sills by this simple expedient.

Lack of the plugs wasn't really an issue unless driving through standing water, but I wired flattened drink cans in place, mostly to inhibit rat ingress, but they also prevented water splashing upwards while still allowing drainage.

I also removed the carpets, and lost them.

Nasty things anyway, but most people seem to like them.