Note: Before you start, your phones Bootloader must be unlocked, if you own a R800i (UK/EU version of the phone) then you can unlock it through Sony's website, if you own a R800x then you might have to pay to have it done, a quick Google search should tell you where to have it unlocked.

-1. Download this ROM (Thanks to markphyton from XDA) [ Register or Signin to view external links. ]

-2. Choose one of these custom Kernel's to flash onto your phone, either one it doesn't matter, personal preference.
[ Register or Signin to view external links. ]
[ Register or Signin to view external links. ]
(Also download the WiFi modules which are located somewhere on each post on XDA for the ROM you chose)

-3. Put the ROM file you downloaded, and the WiFi Modules for the Kernel you chose on the root of your phones SD card

-4. Flash one of the custom Kernel's to your phone using either Flashtool or fastboot, a tutorial will be somewhere on the internet

-5. Once the flashing has finished, boot up your phone and get into Clockwork Mod recovery (different depending on your ROM, do some research)

-6. Flash the ROM you downloaded from Step onto your phone, then followed by the WiFi Modules for your selected Kernel.

-7. Reboot your phone, and enjoy ICS!

Note 2: (There also might be updates, or bug fixes posted on this thread for the ROM, so stay tuned to [ Register or Signin to view external links. ]

READ: I also might be posting a lot more tutorials for Xperia Play users (flashing Kernels/Firmware files and ROMs to your phone) I can also make a tutorial on how to unlock your bootloader if you're using a R800i phone like me, but however unlocking your bootloader removes the usage of TrackID from your phone so do it at your own risk.

Patches

-Patch 1:
Installs newest Adreno drivers for speed increase
Enables 720p recording
Google apps fix (Play store, Gmail, Google Talk etc)
Superuser fix (Force closes, not remembering permissions)
Supercharger fix for speed increase