Or
Download a .deb from here
2) Get qt4-qtconfig
sudo apt-get install qt4-qtconfig
3) Run qtconfig-qt4 (Using alt+f2). Select the GUI Style as GTK and File>Save.
4) Incase this does not work, install these packages:
sudo apt-get install kdebase-workspace systemsettings
Then run systemsettings. Go the Appearance section, and change the Widget style to GTK.