Good question, seeing he has a 2595 which uses TTS'2' voices. British Serena, i thought was only available in original TTS used in 2 and 7 series nuvis for example and now surprising as TTS'3' only for 2013> Prestige & Advanced range. Maybe he actually has a 2597.
I suspect the James and Kate that he has are the VCT voices [non-TTS] of the same stable as American Michelle and Australian Matilda. Here's the links if you want to try them: