[SOLVED] I've just fixed several UEFI installation issues

If you're installing (single OS boot) on two disks (SSD 60GiB for Linux, HDD for /home), you may face the same problems I've had on my ASUS H81 motherboard. I used an Ubuntu 16.04 DVD on the front of LinuxFormat to install (Live USBs can be very painful to get right). I hope this helps:

1. My SSD was mounting as /dev/sdb, the Ubuntu install will only work on /dev/sda. This may have generated the error "grub-efi-amd64-signed package-failed to install". Fix: I swapped the SATA cables around on the motherboard.
2. Having failed for months to get Ubuntu 14.04 to boot in UEFI mode (despite USBs happily booting that way), I realised today that the old 14.04 had installed in legacy (BIOS) mode and that therefore my SSD was formatted in old-style MBR partition mode. Now Rod http://www.rodsbooks.com/gdisk/cgdisk-walkthrough.html has an excellent guide to using his utility to repartition as a GPT disk. Rod is a really great guy to have supplied all this stuff, but wow, it needs an "idiot's guide!"
So, the fix is, boot off a Rescue CD/DVD (this was helpfully on the same LinuxFormat DVD) that has cgdisk and use it to delete all the existing partitions on the SSD, then allocate the first as a 2GiB UEFI (type ef00) one; the second as a 30GiB Linux filesystem (type 8300); thirdly, the rest as Linux Swap (type 8200). Note that this is DIFFERENT from Rod's page above, because he's setting up a legacy (BIOS style) boot.
3. Use the commands:

mkdosfs /dev/sda1
mkfs -t ext2 /dev/sda1

It installs perfectly, just took many hours of reading and fiddling!

I hope this helps,

phoenix