NB. When we last checked (2009), none of the following had been updated to use the BNC XML Edition. The counts they provide all relate to the earlier BNC World Edition.
Adam Kilgarriff produced word frequency list for the BNC World Edition, available from his webpage (see http://www.kilgarriff.co.uk/bnc-readme.html.
Frequency lists for BNC World are also published in the book Word Frequencies in Written and Spoken English: based on the British National Corpus by Geoffrey Leech, Paul Rayson, and Andrew Wilson (2001). The same lists are available online.