Never knew that before; although when we were in Chichester Cathedral on Bank Holiday Monday 6th May 2013 there was a labyrinth, painted onto on carpet tiles, in the North Transept.
This seems to be the place to go for labyrinth hunters: http://www.labyrinthsociety.org/home
Here's a picture from the site of the Chartres labyrinth that they give comprehensive instructions for on the site, and that you can download a drawing of.
They also seem to have all kinds of related resources - music, activities, pdfs, heaven knows what. Well, heaven probably does know what, come to think of it.
This "How to draw a labyrinth" gif comes from them too. It's more complex than the simple one I usually use.