Large gap between menu and sub-menu

Hi, my website name is Anydrive.co.uk.  

I have a menu in the header section.  When I mouse over my menu options, the sub menus appear approximately 1 inch below the menu rather than directly below the menu.  

Can you please take a look and let me know how do I get the sub menu to appear directly below the menu?  Currently, the gap between the menu and the sub-menu is too big.

Thank you

Owen