Since our British justice system means that he'll probably be out in a few years anyway, I suppose you could say that he is doing the honourable thing.
Perhaps the family of the girls should be given a say. Not to say that he should die, but whether they think he has the right to if he choses.
After all, once dead, they will never know why he did it, but then it's highly unlikely that they'll find that out anyway. I guess he probably doesn't know why.
I suppose one needs to decide what benefit anyone can receive from him alive or dead. We'd certainly save money if he died and keeping him in prison for a few years will not change anything.