Well, I have had to tweak this it a little, bit it finally worked fine.
Initlally, the arial.ttf could not be found, so that I had to force the use of courier regular
I'm using the standard default Treeflower theme.
The following does toe job:

cd /usr/share/gdm/themes/TreeFlower/background.png \
/usr/share/gdm/themes/TreeFlower/background-original.png

gedit /etc/gdm/Init/Default

Insert the following lines
cd /usr/share/gdm/themes/TreeFlower
convert -pointsize 40 -font Courier-Regular -draw \
"fill yellow text 1500,200 \" \
`ifconfig eth0 | awk '/inet addr/{print $2 }'`\"" \
background-original.png background.png

between
sysmodmap=/etc/X11/Xmodmap

and
XMODMAP=`gdmwhich xmodmap`

Thanks for the help !!