I've been resisting upgrading from 11.10 (just because I wanted to do a clean install onto a new SSD but I was waiting for the prices to come down a bit first) but my hand has been forced and I went for the upgrade today, from 11.10 to 12.04. Anyway, this seems to have all gone a bit wrong, the graphical interface doesn't load upon boot, I've tried following the instructions from here but with no success.

Rather than spend hours trying to fix it, and as I wanted to upgrade clean anyway, I want to start again from scratch. Well, almost scratch... I had my system mounted on one HDD partition, and my home areas mounted on another partition. So ideally I would like to install 12.04 (or 12.10) clean over the top of my old system but leave home in place, but I want to do it safely, as I believe there are lots of system/config files in /home/user that would need to be migrated to the new system? Plus I obviously want to keep all my documents, photos, etc.

So what is the best way to do this? During the install do I simply choose to mount the home partition at /home and trust it to work itself out? Or do I leave /home in its default location, then somehow move it once everything is installed? (Presumably by booting to a live cd, removing all old hidden/system folders in home partition, moving new /home/user into home partition and editing fstab? This is where I get out of my depth) I have some Linux experience but I am not an expert, so (please!) keep any responses easy to understand!!

Finally, I don't have enough spare space anywhere to move everyone off the HDD before proceeding, but I do have everything backed up on an online backup service, but I would really rather avoid having to download all that again, so a fail safe mood would be appreciated.

I have done a bit of a search for help but not even sure what a useful search string would be.
Many thanks,