>Hi All, I currently have all of the common .NET control classes defined in one ( getting bigger by the day ) file and am thinking of separating them into individual .cs's - does anyone know of a tool on the market that does this ? has anyone here written such a thing ?

CodeRush/Refactor! from http://www.devexpress.com does this, although it's not fully automated. You basically position the cursor on a class and either click on a button that appears or hit a hotkey and it pops up an option to move that class into it's own file. They released a free version, Coderush Express, which might have this functionality (you'd have to check).