how can i get my potterton profile 40e to light?

Try this

http://kaijaks.co.uk/blog/nick/2008/02/10/dodgy-old-boiler

Sounds as if the sensor for the pilot light thinks the pilot is not lit - hence constant sparking and no main gas valve opening - I have very little knowledge of boilers but it may be the 407677 PCB (see web site) or the flame failure sensor thing.

The web site shows how to fix the PCB for about £1 rather than spend £250 having an engineer replace it!

Peccavi
November 2008