At present, I have a multi-boot setup on my PC, with XP on one hard
drive (sda1) and two main partitions on the second hard drive, roughly
50/50, containing Ubuntu HH on sdb1 and Mepis 7 on sdb3.

I now want to get rid of Mepis and concentrate on ubuntu as it is
fulfilling all my needs and enabling me to do without Windows for 90%
of my work. I also need the extra space for programs etc.
Unfortunately, as mepis was a later install, the grub is controlled
from there. I know that I could do a fresh install of ubuntu using the
whole of sdb and setting up the dual-boot with XP from there but I an
loathe to do this as I have already spent a lot of time personalising
ubuntu and don't want to lose all my settings.

Is it possible to re-partition sdb to achieve this and change the grub
to ubuntu? If so, I would appreciate simple instructions as I am still
very much a newbie with linux.