FYI, Atom is not by HTC. It is quite obvious in the design and styling of the device. The successor to O2 mini is Dopod 818. For some reason, O2 decided to go with the other ODM.
A little out of touch, can't remember the ODM/OEM taiwanese company and all of HTC's product name. Surf on the web and check out modaco would provide alot more information..
EDIT: This website useful
http://wiki.xda-developers.com/ and that other Taiwanese ODM is Quanta. Newer, and products overall not so proven. Must have sold their Atom at a very good rate to O2 to convince them to use their device.