Attempt to decode BT’s dialled number to chargeband mapping, by scraping a PDF of the information. At present, this only looks at NTS, Mobile and other Premium-rate services. Does not look at international chargebands, which gets rather complicated, nor does it deal with geographic numbers where you may be on a tarriff that gives cheaper local geographic calling than national geographic calling.

This data is, by the look of it Copyright BT, as the footnote on the PDF currently states.

Other similar files that may be worthy of scraping are Virgin Media’s equivalent, though they have their some of their own chargebands:

http://allyours.virginmedia.com/pdf/uk_non-geographical_calls_a.pdf