How easy are these to buy in the UK? What is the likely cost? Can you unlock a smart phone?
Fully kosher unlocked phones from reputable sources have been available for ages in the UK. Even iPhones have been available unlocked off-the-shelf for ages now. Sounds like you're mentally stuck in the "old" UK of locked phones...
(Kosher in the informal slang context here, rather than having been kissed by a Rabbi....although it wouldn't surprise me in the least if some entrepreneurial Jewish chap was selling kosher phones
!).