Every stadium has a “nosebleed” section. At Wembley, that’s blocks directly behind the stage (like 250-260 in the Upper Tier). You’ll spend the whole show watching a giant screen. Harry will be a tiny ant in the distance.
Also, beware of restricted view seats. Wembley has massive pillars that can block the stage. If your ticket says “Restricted View,” it’s not a joke. You might spend the concert staring at a concrete column shaped like a sad triangle.
