Thanks Nick ,enjoyed the fruits of your knowledge..always been keen,but not that studious.got really annoyed the other night with the bbc weatherman going on and on about the "arctic" air we are experiencing!!! Er not for me,we are in fine frosty anticyclonic air,which is always cold in winter(nice in summer) we all know when we're in "arctic" or polar continental air,chances are we'd have -ve temps even during the day!! Anyway ..glad I got that off my chest.