Show sub-sub categories underneath sub-categories on the category page?

Hi,

I'm wondering if anyone can help with this.. I have done a number of my own configurations and nearly have this cart exactly how I want, but am really struggling with this one particular change. I've looked everywhere to see if someone has done it before and also looked at the code myself but not sure what to change

On the category page.. i.e. index.php?main_page=index&cPath=1

I currently have it showing the category name at the top, then a list of its sub-categories underneath each showing their picture. Each sub-category has its own sub-sub-categories though, so I want the sub-sub-categories to show underneath the sub-categories so that they're all listed on that same page, make sense?

Example...

Designs --> T-Shirts --> Scoopneck T-Shirts

Normally the Designs page would be like:

Designs

T-Shirts | Tank Tops
Pants | Accessories

But I want it to be like this:

Designs

T-Shirts
----> V-neck T-Shirts | Scoopneck T-Shirts

Tank Tops
----> Spaghetti Tanks | Widestrap Tanks

... so that all sub-categories AND sub-sub-categories are displayed.

Also... not ALL sub-categories do have sub-sub-categories, so if they don't have any they should just be a link like they were before. I don't want any products showing on the category page, just every first child & grandchild category instead of first child categories only. I hope this made sense.

Would be really appreciated if someone could figure this one out, thanks!!