Allotments 4 All

Anyone tried these and is it worth it. Seems too good to be true 
http://www.ebay.co.uk/itm/Thai-Yam-Bean-vegetable-Plant-Fresh-5-Homegrown-Seeds-Huge-Vines-high-yields-/271116666846?pt=UK_HomeGarden_Garden_PlantsSeedsBulbs_JN&hash=item3f1fd007de

Ah, yes..=jicama
I've grown it but still without much success. It is said to be ok for UK growing...BUT...you propably need half decent summer for it. I'm not sure if we are able to get quite that size tubers as result though.