Diamond Sheffield Ltd. has just undergone a management buyout. The Diamond brand of dispersions for inkjet inks has been bought by the two executive directors, Pete Callahan and Sue Wright.      “It was our business idea from the beginning,” said Ms. Wright. “We have just brought it back home, re-polished, refinanced and ready for business.”      The change of ownership has been accompanied by a new name. The new company is called Diamond Dispersions Ltd. “We had thought about changing the ...