How to EFI install Ubuntu?

Solution 1:

It is possible that some BIOS's option is disabling the EFI correct behavior. Have you tried to enable the EFI options in the BIOS before booting the dvd? Also, it is possible that the signed lock is causing problems during the boot. Check these things and good luck!

Solution 2:

This is by no means a fully working answer but will be updated as and when I can-that is if and when necessary.

Have a Hybrid EFI system here which means selecting dvd EFI mode and ensuring SATA set to AHCI in BIOS settings will force BIOS to boot hdd in EFI/GPT mode and allow any installer with a suitable EFI boot image to run in EFI mode when booted from DVD device. If there is no valid EFI boot image to load then the BIOS installer will run which would give a MBR partition table installation = legacy.

Have managed to get an EFI windows install but not worked out Linux yet. Am sure the answer is here and referring to this confirms there is no EFI shell or GUI for EFI available because of Hybrid EFI system; which may help explain the "automagical" install of Windows.
Trying to install Ubuntu alongside Windows has not been possible as Ubuntu installer does not even see/detect Windows install - that is when letting run in Legacy mode.

The UEFI specification required for Secure Boot is => UEFI 2.2 and Windows 8 pre-installed machines will use UEFI 2.3.1.
As EFI is predecessor this hardware is not Secure Boot capable. Using a signed key installation media is not going to be much use for implementing the EFI features that this hardware does possess allthough it should not make any difference that is when considering the fact that all U/EFI specification should be or are actually backward compatible. Simply means no secure boot.

Updates will follow. (or alternatively other answers!)