Heating problems !

Have a 2003 BMW 325i with Automatic Gearbox.
I have a problem, first of all, heat doesn't come on until the temperature guage is at the middle, otherwise cold air. When the car is warmed up, still not getting that much heat, it does get warm, but not hot, no matter what the temperature, either at 20 degrees centigrade or 32 degrees centigrade, the highest, it does not get warmer. Also, noticed no eat coming down to the floor. I had the thermostat replaced about a month ago, because I got the engine.
Can anyone please help me with this issue ?
Thanks

What brand of thermostat did u put in it? Plus did you bleed the system properly? What is the coolant level?

Since you replaced the thermostat, I am assuming that you car has sufficient amount of coolant. Otherwise you would have noticed it. There are a couple areas that I would check. One is the valve actuator that controls the amount of warm/hot coolant to pass through the heater core in the car. The other one is the coolant pump. I heard from a friend that some year's BMWs' coolant pump impeller was made of plastic! That sounds crazy, and it is a potential failing point that the impeller just seperated from the coolant pump over time, and coolant can't circulate through the heater core! Hope it is not the latter that you are dealing!

I don't know which brand, all I know is, it was replaced, and no engine light after that !

Pump is not the problem. If it failed, your engine would overheat quickly.
And composite vaned pumps last a good long time. Bad ones are long gone from early cars.
You probably need to bleed the air out of the system. usually needs it more than a couple of times after refilling the coolant.