Where can I buy Najing Rice (black rice)? in UK?!

I would try Mung Mee in Lancaster near the bus station, there is also a stall on the lower market.
If you are going to Manchester, try the chinatown area, as they have several far asian shops

ive never heard of najing black rice but ive heard of black glutinous rice
http://en.wikipedia.org/wiki/Black_rice
the properties are similar- turns into dark purple when cooked...or so when i buy my black glutinous rice and cook it into black sticky rice with coconut milk (thai desert)...if thats what you are looking for search asian groceries stores.