SHARES in Berkeley Group have tumbled along with those of other housebuilders to 204p, against a high of 345p earlier this year. SG Warburg, admittedly broker to the company, reckons the shares are now a buy on a multiple of 12.9 times forecast earnings for the current year. Unlike its rivals, Berkeley has little debt and good cash flow. It was smart enough to sell its holdings of unbuilt land before prices crashed, only to buy back later at a lower cost. The company is one of the few builders to pay a decent dividend as well.