Switches are cheap on ebay so try one but it could be the window motor itself.
Mine was doing exactly the same, wouldn't go down but would go up.
Before you try a switch, when the window doesn't work quickly remove the door card, gently remove the membrane and thump the motor
if it goes down then you may need the motor....
When you see the price of a new motor you may want to try temporarily what I did. There is a big air gap between the door card and motor. So i chose to affix a random object onto the door card so when the motor wouldn't work I could hit the door card which in turn would make contact with the motor. Never had to do it since as the motor has always behaved itself!!
A second hand driver's side front window motor is quite rare to find especially if you have one touch - Euros is listing an OE rear at £258.00.
I too bought a switch first so you are welcome to try it out
