Iam renting a house and have a letting agent who deals with it?

he is the person i go to when jobs need doing/reairs etc HOWEVER I HAVE HAD NO END OF PROBLEMS WITH HIM ,WORK DOESNT GET DONE WHEN HE SAYS ITS GOING TO BE ,WORKMEN DONT SHOW UP AND MY TIME IS WASTED SOMETIMES I WAIT FOR DAYS AT A TIEM HE NEVER CALLS WHEN HE SAYS AND NOW MY CEILING HAS CRASHED THROUGH BECAUSE OF A MAJOR LEAK IN MY UTILITY ROOM WHICH I CALLED HIM ON STRAIGHT AWAY AND I WAITED 3 DAYS FOR A PLUMBER WHICH MADE THE MATTER WORSE HENCE THE CIELING FALLING THROUGH ONTO ME.THERE ARE HOLES IN MY FLOORS UPSTAIRS WHERE WE WALK AND LOADS OF OTHE RSTUFF QUITE FRANKLY I AM AT MY WITS END AND WANT TO KNOW WHERE I STAND LEGALLY AND CAN I WITH HOLD RENT REFUSING TO PAY UNTIL ITS ALL DONE MORE OVER MY PERSONAL BELONGINGS HAVE BEEN DAMAGED MY CHRISTMAS SPOILT AND STILL HE HASNT BOTHERED TO HAVE ANY CONTACT.