Xpert Systems, the Dublin-based technology group, has expanded its business in Britain with the acquisition of Castleton Communications for €5 million (£3.9 million). Castleton is an independent network integrator based at Cleveland, north England, and employs 90 people. Founded six years ago, Castleton provides design, installation, integration and support of network infrastructures, including Internet/intranet, voice, video and data. It has strong collaborative links with major technology manufacturers including 3Com, Cisco and Lucent and has more than 400 customers.