grub install fails on efi partition with pre-installed win8.1

I'm trying to install 14.04 alongside Win8.1 preinstalled on an Acer V3-772G laptop. 8.1 is installed on the HDD and I've added a new SSD to the laptop for 14.04. The ubuntu installer does not find the 8.1 install so I tried 'Something Else' making the SSD my / mount and selecting the EFI boot parition from 8.1 as the boot manager installation location. The installation then fails while trying to install grub at this location.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubiquity 2.18.8 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 3.13.0-32.57-generic 3.13.11.4
Uname: Linux 3.13.0-32-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CasperVersion: 1.340
Date: Mon Oct 6 12:28:14 2014
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash --
LiveMediaBuild: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)