As I said on another thread, don't panic, SEEtickets are a decent outfit, they're not conmen. IF you're tickets haven't come by Friday or Saturday, then speak to them on the phone. They will cancel the missing tickets & re-issue new ones (the same seats) which will be collectible from Wembley Box Office.
I had this last year with See, and they were very helpful.
Exactly. Ticketing is a major business these days and these companies deal every single week with events bigger than Southend United vs Wycombe Wanderers.
They will deal with any issues so just relax.