These kinds of errors happens if the VS designer cannot resolve the controls, by adding the <pages section to the Web.config of your project and by adding the references it should be able to resolve those, but VS can be finicky, you might need to open the .ascx and .aspx pages in your project and try to go to design view, you may get errors in design view but it may also make the designer see those references and then it may compile after that.
Hope it helps,
Joe