I discovered a phenomenal amount of debris behind front wheel arches and under the panel. I was just shocked to find that. I managed to suck it all out with vacuum cleaner from the wheel arches and I had to partially remove the scuttle panel to clean the area underneath it. Clearly this is a design issue as the dirt has nowhere to go. I have installed fine plastic net as per picks attached. The net is secured with velcro tape to cover the opening above wheel arches. Two plastic clips on the scuttle panel are used on each side and the rest of the net is just tucked under the ruber seal. The only concern I have is about the size reduction of the air intake openings on the scuttle panel and potentially less air getting in. I am not sure if this can have any detrimental effect on any components of the heating/cooling system. The aim is to have the debris sitting under the bonnet where the net is installed and getting it cleaned will be much easier. I don't think the dirt can move to other areas of the engine bay from there due to the placement of rubber seals and foams. In any case, if it does not work as expected, the nets can be removed easily.

Very good idea, especially if you park near any trees, although I've owned cars that don't even have any holes in those areas and still after a number of years you end up with a load of compacted mud a behind the front wheel arch liners so its a good idea to clean them out every now and then