it won't do as well in competition if you don't use continental ingredients. That said, it'll be fine.
I am a strong believer in using the most local ingredients possible however, I must grudgingly admit that when it comes to german lagers, german malts make a huge difference.
My marzen recipe is pils and 10L munich. it's very tasty when I use great western or gambrinus malts but it's a whole different animal when I use weyermann. it's really astonishing the difference it makes.