I eventually got it working! I tried formatting the partition into all sort of formats through gparted, but I would eventually get the MediaKit. I did some more googling, tried a couple of things, and then stumbled across this link
http://blog.thedeltaflyer.com/2013/01/dual-booting-windows-8-and-mountain-lion-natively-using-efi/, which tells you how to set up a microsoft reserved partition between the EFI and mac drives. It seems that the MSR partition gives ML the freedom to re-format a partition to HFS without wanting to re-write the entire partition map. I'll share my workflow here...
1) set up EFI, microsoft reserved (MSR) and unformatted partition in the command prompt found on the Windows 8 USB installer (see link above for details)
2) go back to gparted live USB, format the unformatted partition into two sized partitions that you want for mac and windows. type of partition doesn't matter as we will be formatting again in the next step.
3) booted up mountain lion installer (i'm using 10.8.4 using r1928), formatted mac partition to HFS+ (I previously could not format to HFS+ without MediaKit error).
4) At this point it disk utility refused to see my fat32 EFI partition correctly, so I went back into gparted and re-formatted EFI partition to FAT32. I guess I could have done this at step 2, but I did it here anyway.
5) Back into mountain lion installer, installed ML onto mac partition. no problems.
6) rebooted surface, using windows 8 install USB to format windows partition to NTFS and then installed windows. Now windows is default boot.
7) booted back into new ML partition using ML installer (coz I still need to use Clover), and set up kexts for power management and installed audio from SRU_Jake's setup zip. things are good.
Now I need to install clover onto my EFI partition, and this is where I get stuck. Gendo, I followed your guide from post #50 up to step 34) and got confused where you suggest booting up the surface whilst holding down the right arrow key.
What does holding the right arrow key on boot up do? I can't seem to get it to find the Clover installation on my EFI partition, and couldn't find any documentation about what to expect when holding the right arrow key during the boot process. I also tried booting up clover from the ML USB installer and using it to find clover on my EFI partition but that sadly didn't work either.
So right now I am using the ML USB as my bootloader which isn't a terrible thing, but if I could get it to recognise the EFI clover installation that would be ideal.
Does anyone have any suggestions?