Very Quick Question... Product Listing - What page to edit??

Hi all, i'm making good progress with our site, but just one page eludes me..

I need to edit the category products listings layout, but can't seem to find the file to edit..

When you click on a category and it lists the relevant products in that category, those are the pages i want to edit. I presume it's a global edit, such as in the case of product_listing_display etc..

http://buybenchmark.co.uk/index.php?main_page=index&cPath=26_265_266

I know someone will know, so give me a shout back if you can help

thanks
Gary

PS any feedback on my site would be much appreciated..

When you say edit, what are you wanting to do specifically?

Just looking to change layout, as i've done for the product_listing_display.

And also, i guess there maybe be entries in the css file for spacing etc?