What if a bit of rainwater is coming into the interior of my 97 XK8 Coupe (it is!). I don't think it's the drivers side door seal causing this. Someone told me recently it could be a flaw in the wiper drain area. Not recently, but in the recent past, the triangular area containing the brake fluid reservoir would fill up with water.
Any ideas?

There is a drain at the forward inside corner of the compartments on both sides, and they often become clogged with debris. See if a vacuum cleaner attachment will reach. I made up a tube with 3/4" hose wrapped with tape to fit the vacuum hose.

That's sounds reasonable RJ,
I'll look into it. Thanks!

To unblock drain holes I use a strong long zip tie.

Like this Click Here

Some use a wire coat hanger for this as well.

In addition, I seem to remember there is a rubber tube involved in the setup. This tube collects water from the cowl and directs it out of these bins. This rubber tube has a tab that attaches to a peg at the level of the bin lid (fairly high up). It is not uncommon for this tab to come undone and let water in the bins.

Best of luck, keep us posted.