I realized a day or two ago that the advice I gave Mowcius is needlessly complex. The 40x4 display can be thought of as two 40x2 displays each with its own hd44780 controller chip and with all the pins in common except the enable line.
Yeah. I had not had time to look into it in more detail so you saved me some time 
I will try that code later if my 40x4 wants to play ball.
Mowcius