Yes you can use VS Express for the PC version of your plugin.
Would you also know if there is an emulator or equivalent for illustrator so I can test the plugin while developing? I'm being asked to create a plugin but dont actually have illustrator and didnt really want to purchase it for one project.
No, there is no emulator you can use. You can get 30 day trial versions of Illustrator. If you are targeting Illustrator CC, it is a subscription product now so you just pay monthly for as long as you need it.
Thank you Leo. Thats a great help.