I've lived in Northwich all my life and this is the first I've heard of this incident. I'll ask around.
Far more common in local WWII parlance are the Luftwaffe aircraft that came down near the old Octel factory. The story goes that some of the surviving crew had to be rescued from locals armed with pitchforks!
I'm also aware of an aircraft (RAF training flight?) that crashed into land opposite Hartford shops. This land is currently being developed for houses and there was some recent controversy as to its safety due to the crash, probably unfounded.