NikT: Smart ultra does not support 850MHz 3G, so is not suitable for use on Spark/Skinny.
Thanks for letting me know, but damn that's a pity (for us consumers, not Voda of course!). I'm glad I asked as I stupidly assumed it would support Spark given I understand the Prime does (and this is despite me knowing they're made by different manufacturers).
Back to the drawing board for the best-value mid-range phone that also works on Spark (kinda reliant on the Spotify package so not keen on moving)...