Is it possible to change the Bluetooth UUID (the 128-bit value) on my iPod (Currently running iOS 5.0)? or is this a factory locked value?
No it is not possible. No known private API or jailbreak methods to do so AFAIK.
The UDID is locked, but it is possible to spoof a UUID, as for an Bluetooth UUID, I'd think so but I'm not sure there's anything readily available i.e. in Cydia to do so, only a general phone UUID spoofer.