I was at the pub last night with my mate who installed OS X on my Dell telling him more about the problem. So, I had my mini in my bag and thought.. what the hell, I'll show him how it doesn't come back from sleep.
The short story is, my mate was able to fix it and I couldn't thank him enough, this is what he did:
1. Running "kextstat | grep PIIX" would always return "(9.0.0)" for the version, even though others said it should be "(2.0.0)". This was doing this even though I ran DellEFI 1.1 final in various ways and downloaded a ZIP packaged in late 2008 with that kext from insanelymac.com, this never seemed to change.
2. My mate did some Googling (courtesy of the inbuild 3G on Voda
) and read a forum post saying that the AppleIntelPIIXATA.kext should ONLY be in /System/Library/Extensions/IOATAFamily.kext/Contents/PlugIns and not just /System/Library
3. Further more, the instance of the kext I had had the "@" symbol in it (I don't know how my mate did this - it was via terminal though) meaning OS X didn't trust it (the graphical version of this is "You downloaded this off the internet, do you want to run it?")
4. Multiple reboots still didn't fix the 9.0.0 issue, so we ran DellEFI again.
5. Again, no fix yet. So my mate did a "diff" of the kext on my system and the one in DellEFI 1.1 and realised they were totally different
. DellEFI for some reason wasn't pproperly updating my kexts so he manually extracted it from the DellEFI package and replaced the one in /System/Library/Extensions/IOATAFamily.kext/Contents/PlugIns
6. He then forced a boot rebuild but I'm sure it would have done this anyway and rebooted.. This fixed my issue
Hooray, now I can use my Dell Mini like a normal person without a 1.5 minute boot up and a 30 second shutdown