Persimmon reported half year profits up 38 per cent and said its order book was running 21 per cent ahead of last year as the government's Help to Buy scheme boosted visitor numbers.The house builder has taken over 1,700 reservations under the Help to Buy initiative since it launched in April. It said visitor numbers to its sites were up 15% year to date and cancellations were also running at historically low levels. Its order book stands at £1.3bn compared with £1.0bn at the same time last year.Persimmon plans to open 85 new sites before the end of the year and it invested £236m in new land in the first half.Chairman Nicholas Wrigley said: "To deliver the volume to meet this increased demand we are maintaining our strong investment in land and stepping up our investment in construction."The company, which returned £228m to shareholders at the end of June, reported pre-tax profits of £132.9m in the six months to June 30, up from £96.5m last time, after completions rose 7.0% to 5,022.TB