RE: Dell XPS 13 9350 (November 2015) Install Ubuntu 15.10
Thanks to @Buuutch, confirming this has worked.
I was attempting to dual boot Windows with Linux Mint 18.1, but the Mint installer could not see my SDD.
Switching from RAID to AHCI using the simple steps given above, left my Windows OS intact, so no re-install was required.
Thereafter, the Mint installer was able to see my SSD and I was able continue with the normal installation.