You should be able to remove the carpet from the floors like you'd remove a mat in an American car. The pad is glued to the back of the carpet and it just lifts out.

There is sound deadening material on the firewall section, if that's what you mean. But to get to the metal floor maybe a few snaps under the seat?

Take 'em out, lay 'em in the sun.

The sunroof drains may be a culprit, or the window seals.