Hi,
could you explain in more detail what you want to achieve? Do you want to see what is the distribution of most frequent words from BNC subcorpus in your corpora? Or do you want to look for stylistic similarities between texts in each of your corpora and texts in BNC subcorpus? For the second task you would also need information on the distribution of the MFWs in the subcorpus and not just general frequencies.
And in general - your frequency list is formatted differently from stylo's expected, so no matter which task of the ones I mentioned it is, it will need some transformations should you want to use it.
Best,
Joanna