Seymour Pierce has downgraded its rating for B and Q owner Kingfisher from 'hold' to 'sell' and trimmed its target price from 290p to 240p following the group's first-half results which were significantly affected by the weather and foreign exchange losses."Despite downgrades in recent weeks, interim results to end of July are disappointing and at the bottom end of market expectations," said analyst Freddie George.Adjusted pre-tax profits came in at £371m, 15.5% down year-on-year and under Seymour Pierce's forecast of £385m."All markets, but in particular the UK, reported disappointing figures down against the previous year," George said.The broker has provisionally lowered its current-year pre-tax profit estimate from £810m to £740m, taking earnings per share (EPS) forecasts down from 24.7p to 22.6p."Some of the problems are one off but one worries that some are also structural."While the company has a number of self-help initiatives, George says that its two core markets, the UK and France, are mature and will required major restructuring.George added: "The stock has held up well over the last quarter despite a steady trickle of downgrades and on the basis of our revised forecasts is more than fairly valued. On the basis of our forecast it is valued at 12.0x FY13 earnings which we believe is too demanding giving the difficult outlook, with a prospective yield of 3.5%."Shares were up 0.33% at 273.20p by 09:50 on Wednesday morning.BC