[andy]

The Upptalk number is meant to be permanent (choice of UK, USA or Germany), though mine did go missing for a few days until support or their technical people fixed it.

As caller ID number for calls it uses your own number you used to register though. I haven't tested that for sms yet. I asked about being able to change caller ID later, perhaps to the Upptalk number itself. They were having some issues on that subject at the time, so I'll ask again in a while.

It seems more reliable for receiving sms than the Tismi numbers used by Pinger and TextMe, but I have not tested from all UK networks