Okay all, I got it installed and working fine. The problem is both with the way openSUSE installer formats the partition and with the way it installs grub.
How I did it was to download the Ubuntu Jaunty (9.04) LiveCD and partitioned the drive with that (/dev/sda3 (ext3) as "/" root and /dev/sda4 as swap). I then booted using the openSUSE installation disk (Gnome LiveCD in my case) and installed but made sure not to reformat or modify the partitions and NOT to install a bootloader.
Once installed I rebooted into the Ubuntu LiveCD and from a terminal ran
Into that I put:
grub> root (hd0,2)
grub> setup (hd0,2)
# mount /dev/sda3 /mnt
# vi /mnt/boot/grub/menu.lst
I then rebooted the machine and Sync'd the partition tables through rEFIt and booted openSUSE (fails to boot the first time, just reboot).
kernel /boot/vmlinuz root=/dev/sda3
Now it's time for this.
Hope this helps others.