The only difference between the UK and North America versions of all OBi ATAs and phones is the PSU wall-wart in the box. The UK ones have the BS 3 pin plug. The UK ones are rated for 100 to 230 volts. I expect the others are too but have never one.
As regards firmware, features and default settings, the ATAs and phones are completely the same. There is an XML file available for download which will select the configuration parameters to give UK tones etc.
The presence or absence of a GoogleVoice logo is immaterial.
The Obi200 is a current model. I wouldn't read anything more into it being out of stock at Amazon UK other than its literal meaning.