7/7 and 7/21 Operations Unrelated?

Via the Counterterrorism Blog, the (London) Independent is reporting that British counterterrorism authorities have so far concluded that there is no common operational link between the terrorist cells that executed the 7/7 and 7/21 bombings, respectively.

The alleged plotters behind the July 21 bomb incidents in London are thought to have been "copycats", targeting Tube trains and a bus.

A "copycat" operation in two weeks? Surely this is a misleading way to describe it -- with respect to timing, perhaps, but at a minimum there had to have been a separate training and logistical infrastructure for the 7/21 operation that predated the first attacks. "Independent" is probably the better word.