Arcadia is to restructure its mainstream business unit, Retail Week reported today. The unit, headed by Nick Hollingworth, will be split into five management regions rather than three as it is at present. The Dorothy Perkins and Burton Menswear chains will be affected by the changes. An Arcadia spokesman said the decision would improve the business. "It will enable them (regional managers) to give better support and make the unit more responsive," he said.