General Water in the front boot

[crazypierre]

Hi there,
Been noticing water in the front boot area after it rains.
It's coming in from under the fuel tank and then into the spare wheel well.
I also find the top of the battery gets wet.
Any ideas how it's getting in there?
There is a lip all the way round the opening so I can't see that it's coming over the lip.......
But unless the windscreen wiper grommets are letting it in, I can't see where else it's coming from...
Thanks
PC