Well done!
It's an amazing feeling the first time isn't it?
Although most of us grizzled long distance riders think nothing of going out for an imperial century or a metric double (or triple, or quadruple etc. etc.) I think it's important to be reminded just how much of an achievement it is to reach the magic number, and I absolutely love hearing about people doing it for the first time as it brings back the feeling and I absolutely love seeing the elation of people conquering a goal. I'll always give more high-fives to the first timer than the hundredth timer ;-)
I wish many happy miles ahead of you