Run the car upto temperature then pop the bonnet, there is a black coolant hose that runs into the cabin, next to the brake fluid reservoir, on the pipe is a bleed valve. Use a large phillips screwdriver, loosen the plastic screw a little (don`t remove as you WILL get BURNT) until coolant starts to seep out. then screw back in hand tight only, this should cure your no hot air problem. ( you will need to have you temperature controls set to HOT & blowers on)