Now now, Ian, I did say that Lankyman's guess – 'Is it a squeeze between the Minarets on the high level route, Lancaster Hole?' – wasn't too far away!
langcliffe has it with 'Entering chamber near Lancaster end of Manchester Bypass?' though tobyk was pretty close – I guess you two had better fight it out for who wins.
I can’t really compete with Langcliffe on the intricacies of cave locations, but knew just guessing ‘Manchester Bypass’ wouldn’t be specific enough. Fair enough then, where’s this sump?