I want and did some investigation work on mine this morning, and found that the water is leaking under the hatch. I found the sealant used hadn't held on the 2 front corners of the hatch cover, and being concerned that winter is upon us, didn't want to wait to get it in to a service agent. Instead I went down to Bunnings and picked up a couple of tubes of Sikaflex Marine grade, in white. Home from bunnings I set about removing the hatch, which was a case of the inside popping off, then undoing the 12 screws (3 per side), and popping the top of the hatch out. From here I cleaned the remaining sealant off the hatch and the roof (by standing on a crate in the van and standing up throught the hatch hole), and found in numerous locations it hadn't held. After giving the areas a good clean, I proceeded to reseal the hatch and then pulled down into place in the roof. Re-installing the internal piece and the 12 screws, I proceeded out of the van onto a ladder, and added a further bead of sealant around the outer edge of the hatch! Quite difficult to reach off a ladder, especially with the wind up aerial on one side and the solar panel on the other, but have hopefully sealed it up for good!
Cheers Ben