Heater not working right

Hi, I took my daughters car down to our mechanic for him to have a look today and he has said the problem is in this part under the dash where everything needs to be taken out to get to it. To get to it id have to remove console panel upper, remove instrument cluster finish panel and then remove heater control and accessory assy. Mechanic said it is not a cheap job to do.

Hi Joe and thanks for your promptness in getting back to me. Yes, the blend door is what he seems to believe to be the problem and not overly eager to sort that suggesting that might be a better idea to wear a jacket in the car due to the cost and the car having to be left there over a week so he can work on it a bit at a time whilst doing other customers. The other day I undid both of the hoses leading into and out of the heater core and gave it a flush (and refilled the coolant level) which helped to the point that the air was slightly warm enough to defog the windscreen and side windows. Both the hoses entering and leaving the heater core are hot. I have undid the cable as requested and checked to see if the level of temp adjusted which it really didn’t aside from the slight change already getting but can hear the blend door moving properly from one side to the other when shifting it from cold to hot settings by hand and when cable has been reconnected. I also took the car down to our local shopping center carpark seeming was raining heavy here and removed the glove box and took this photo which don’t seem to easily point out the location of the blend door actuator that some YouTube videos have suggested as a possible issue. I wouldn't know where to start to get access to it as all of the videos seen have the blend door actuator clearly visible. The car temperature gauge according to my mechanic works sitting midway between cold and hot which is normal for this model Toyota Corolla.