There's no (public) checker I know of that shows line length either, they all take into account additional factors such as line quality, external noise and crosstalk.
Best estimate you can get is off an engineer's JDSU, which can directly measure line characteristics, best estimate you can get without kidnapping an Openreach engineer (or their kit) is by finding your cab off one of the leaked spreadsheets and using a map.
Edited by qasdfdsaq (Mon 30-Apr-12 18:41:51)