Luke Johnson, the Channel 4 chairman, is looking for a buyer for his 30% stake in Integrated Dental Holdings, Britain's largest chain of dental practices. Hawkpoint is looking for a private-equity group willing to acquire his holding. IDH hopes to raise fresh capital to help fund its expansion. Johnson led a consortium to take IDH off the stock market in 2004 in a deal worth about £25m. Today, the business is valued between £50m and £70m.