As far as I know Arriva three is Guardian. The entire block is now developed, but at one time before Guardian came along it was supposed to be three towers that look like the Arriva tower.
I liked Arriva when it was built, but it's looking a little asymmetrical and dated next to the freshly built Guardians. There is potentially room for one more tower on that stub in the SE corner of the podium though I suppose. "Where there's a will..." I just don't think there is a will.
Funny, I know what you mean. Arriva was awesome looking at first, but next to the Guardian towers it does look awkward. I still don't like the top of Arriva.