Increasing Ubuntu (12.04) partition size

I'm running a dual-boot Windows XP/Ubuntu system, and I'd like to increase the size of the Ubuntu partition at the expense of the Windows partition.

I've already shrunk the Windows partition, creating a large unallocated space between the Windows and Ubuntu partitions. See screenshot below.

I'd like to move my Ubuntu partition to the start of the unallocated space, and then increase its size to encompass all of the unallocated space.

Once I try and move it using the GParted liveCD, but it tells me to expect big GRUB issues since I'm moving my Ubuntu partition's start sector.

What is it that I should expect, and how do I handle it?

It's OK, you can easily recover GRUB after the move operation by running boot-repair from a LiveCD/USB (but first you should prepare one if you haven't yet).