Grafton Group, the DIY and building supplies company, has reported a slight increase in revenues for the first half of 2011, with a strong performance in Britain offsetting weakness in Ireland.Group turnover was €997m (£893m), compared to €979m in the first half of 2010.The firm, which trades under the Buildbase, Plumbase, Jackson and Selco brands, increased daily turnover in the UK by 4.7% but Irish turnover for the half year was down by 6%.The firm said in its update: "The trading environment in the group's key markets is proving slow to recover to more normal conditions in light of the continuation of weak mortgage lending and low levels of consumer confidence."The market treated the news harshly, with Grafton down 6.23% in early trading at €3.13