vauxhall corsa ?

my 2002 corsa 12. sxi mists up all the time and even putting the heater on full dosent help heater seems cold all the time unless temp gauge is at half way any sugestions on what it could be and have you come across this had timming chain done at fifty thousend has done sixty eight thosend now have had this problem since timing chain was done regards
steve

steve sales
February 2010