Resizing and moving OSX partitions in Disk Utility

So, I have a Mac Mini with a 160GB drive (it's an old model but it's only for testing). It had 4 versions of OSX on it but one needed more space so I removed the oldest version (Lion) and want to keep it to "latest", "latest-1" and "latest-2".

I've got to the situation where I now have the 3 OSes I need and I've managed to resize the partition for the one which was full so it now runs. But I'm left with a load of free space that I'd like to split between the others so that they don't fill up either.

Hopefully it's clear in the screenshot, but when I want to do this resizing, I have this situation where I can only select that single "partition" and I can't resize it. I can resize the Mavericks partition itself OK, but because that grey section can't be resized, I can't move it or resize the Yosemite/Mountain Lion partitions

mac-mini:~ user$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *160.0 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Yosemite                42.8 GB    disk0s2
   3:                  Apple_HFS Mavericks               50.9 GB    disk0s3
   4:                 Apple_Boot Recovery HD             650.0 MB   disk0s4
   5:                  Apple_HFS Mountain Lion           37.7 GB    disk0s5
   6:                 Apple_Boot Recovery HD             650.0 MB   disk0s6

diskutil from the command line doesn't show a block of free space, but I can see it in the GUI Disk Utility, I just can't do anything to resize that grey area to match the size of Mavericks, which I think I need to do in order to change the "split" between the partitions and add more space to Yosemite/Mountain Lion.

Any other tools I can try apart from Disk Utility, preferably freeware or time limited trials since I'm only going to need to do this once?