Flashing the UK firmware to locked bootloader R800X is the same concept behind the Droid X having a locked bootloader but still having custom roms.
The reason we dont have any custom roms or overclocking for this specifc device however. (or so I've been told) Is because the developers aren't Americans and use the R800I unbranded phones so they never spend any time working on helping the majority of users
Man I just wanna help you out. The r800x was not overlooked or left behind by the developers. You should rephrase because I have gotten lots of help/support from the developers in the Xperia Play community. The bootloader on GSM xperia plays can be unlocked via SE's website and constantly has all current sources and new sources to work/build from. Now heres where Your problem comes into play, the CDMA r800x does not have a free easy way to unlock the bootloader and sources for r800x were only just released. So the developers did NOT have the right sources they needed to make reliable roms/kernels for us.
However, There are a handful of custom roms that will work on r800x and there is a CDMA r800x kernel (kernel is bootloader unlocked only of course)
At the end of the day, if your bootloader isn't unlocked, then plain and simply, your missing out !