The government allows people to "self-define" as follows...
A1: Asian-Indian. A2: Asian-Pakistani. A3: Asian-Bangladeshi. A9: Any other Asian background
B1: Black-Caribbean. B2: Black-African. B9: Any other Black background.
O1: Chinese. O9: Any other ethnic group
M1: White & Black Caribbean. M2: White & Black African. M3: White & Asian. M9: Any other mixed background
W1: White British. W2: White Irish. W9: Any other white background.
Unfortunately you are not allowed to identify yourself as:
Black-British, Asian British, White-English, White-Welsh etc. All you can say is that you are "Other."
What I find incredibly disconcerting is that if you work for (or even become involved with) a public organisation, you have to define yourself not only as one of the above, but also by marital status, sexuality, religion and age every time you apply for anything, be it promotion, a training course or transfer within the organisation!