[ubuntu_mate] Simple install to move from MATE to UNITY 16.04?

Hi - I'm relatively new to Ubuntu though by no means new to Linux, having worked exclusively in it for seven years now. I've been using Ubuntu MATE for some weeks. I like it, but having checked out a pre-release ISO of 16.04 I'd like to move to that when the final release comes out in few days' time. What I want to do - and I've done before with another distro - is just to install the OS on the existing / partition, leaving my other partitions, including my /home partition, unformatted and untouched. I'm not sufficiently familiar yet with the Ubuntu installer to attempt this without some assistance. Can anyone here help?