Partitions stuck, cannot edit in anyway (Retina iMac 2014)

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I have a Retina Late 2014 iMac
I went to install Windows 8.1 using Bootcamp and run into an error message saying GPT or something along those lines. It wouldn't let me install to the partition Bootcamp had setup. Feeling frustrated and confused I used the Windows 8.1 install to start deleting all the random partitions I could find. Quite oblivious to the fact I was deleting my Fusion drive, recovery and other partitions that are important to my iMac's functioning.
It still wouldn't let me install windows 8.1. I restarted and realised the damage I had caused. Finally I managed to get windows 8.1 to install. But I no longer had a OS X installation.
I followed the instructions here from my other Mac to create a bootable yosemite usb installer and start fresh.
Here my problem starts.
While I'm able to successfully install Yosemite it's no longer using the full 3TB of my fusion drive. It's only using 1TB I allocated it earlier in bootcamp. The remaining 2TB is in a partition called "03".
In Disk Utility from the Yosemite installer, Internet Recovery Installer & within Yosemite itself. They all have the same problem. I'm unable to do anything with those partitions. I wish to make my "Macintosh HD" partition use the full 3TB again.
Or be able to restore my mac as it come from the factory with the partitions set up correctly.
As you can see the + and - buttons are greyed out... the functions I believe I am supposed to use is all greyed out through out all the items. I have tried everything imaginable in Disk Utility from all three places (Yosemite installer, Internet Recovery Installer & within Yosemite itself) with no success.
It appears I have really messed things up.
Any ideas?
thank you very much in advance for helping (:
I think I found the solution.
To anyone else having this problem where Disk Utility won't allow you to start fresh with partitions sometimes.
I used Gparted ( ) and it managed to help me fix this problem. Now my drive is one partition almost like when it left the factory.
I installed Yosemite onto it and it's working a treat.
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