The Launderette Equation

There must be a scientific equation for how posh an area is versus how close is the nearest launderette.

i.e

• Posh area (Broxbourne) = no launderette. Zero. (An N of 0.)
• Cheshunt. Twenty minute walk to the mooring, but twenty five minutes if you have to wait at the level crossing . 

(Local house price) / (commuter train fare to London) x (N) = distance to launderette from mooring.

Further research is required to ascertain N and calculate the distance of the boat from the launderette.