I was pretty sure Ben and Hannah broke up because I'd been semi-spoiled, but I didn't know how or why. The YouTube video I watched described it as "Hannah picks Belle over Ben" and I was SOLD on this idea already rofl, and in theory I love love love the idea of Hannah "picking" Belle over Ben and Harry and the various assorted douchebags in her life. I was SO certain the series would end with Hannah/Ben and Hannah retiring and I was really, really wary and am very impressed they didn't go there.
HOWEVER, I am pleased with them Going There in the end, I must say. It's a shame the fourth series was such a hot mess -- and omg all the pretty pictures I see from it are TEASING ME because I am like "I want to preserve my fondness and image of this show as the awesome show it was in s1-s3 BUT BILLIE PIPER YOU SO FINE" -- but at least they ended it on something that is significantly more of a badass moment for Hannah/Belle than the easy out they could've had with Ben.
And now in my headcanon in a couple months time Belle will call up her BFF Bambi to talk about this weird client she had who just wanted to listen to Snow Patrol and cuddle.