Thanks to some very kind folk I am now building up an interesting list of names that people have for these 'fortune tellers'. The name fortune teller seems to be used in the UK, USA and New Zealand, but there's lots of variations to be found, here's the ones i've been told so far...
Salt Cellars (thanks Sarah)
Cootie Catchers (thanks to numerous Americans)
Himmel und Hölle (thanks to Johanna from Germany)
Chatterboxes (thanks to Jen)
Ravas (from Lia in Romania)