mount second disk named vgubuntu root

Indeed the problem seems to have been having two different drives with the same name. It is probably possible to follow a variant of the instructions above to rename the LVM of the root partition but what I ended up doing to solve the problem was much simpler.

I connected the old hard drive to a friend's computer which didn't have such a logical volume (wasn't even running Ubuntu). And after entering the encryption password I could easily rename the LVM.

vgrename -v vgubuntu notvgubuntu 

The hard drive would no longer be bootable as the grub and initramfs would not longer match the LVM but I didn't need that I only wanted to be able to mount the old hard drive and copy data off it.

Once the logical group was changed the hard drive mounted seamless on my new laptop.