Wet drivers footwell carpet mk1

I know this has been raised a few times now but the carpet on the drivers side footwell is letting water in from somewhere! Its not any of the drain holes
along the sills or behind the the seats as i have checked them and they were all fine. Have fitted a new roof too so thats not the problem either. Theres no sign of where the water is coming in from. Have heard they maybe some drain holes under the plastic cover in front of the windscreen. If so could they be the cause of the problem and if so does anyone know how to take it off to clear them out? Thanks

 The rubber seal that runs up the A-piller incorporates the drains for the top corners of the roof. At the top, there is a collection cup, which runs down a tube in the seal, and dribbles out at the bottom over the sill.

 
 
With care, you can run a wire down it to check its not blocked. The two front seals in the hood frame are also problematic. Its possible that the roof fitted has not refitted these back in the correct position. The stainless steel channel in which the seal sits can be adjusted from side to side, using some screws. If a new roof has been fitted, its possible that you now need to retighten the main catches on the header rail; the roof will be initially very tight, and the catches may have been adjusted to compensate. The hood material stretches and settles over time, so now you will need to retighten. Finally, it maybe that the hood frame seals have had it; over time, they loose their shape. Replacements are quite expensive.
Here are some how-tos:
http://www.mx5oc.co.uk/forum/forums/t/272.aspx
http://www.mx5ocforum.co.uk/viewtopic.php?t=64948