Their letters are deliberately over aggressive and threatening. Just ignore them, everything on them is fake (even the names and figures). bbctvlicence.com
Is a brilliant site, the guy has archived every letter he's got from them. You can see how the automated system loops round. The pages explaining the finer points are pretty funny too (e.g. The fictional authors of the letters and ever changing signatures). The most amusing part is the bbc's scramble to buy up the other domains similar to his.