Have you read The Brentford Trilogy by Robert Rankin? (The Antipope, The Brentford Triangle, East Of Ealing, The Sprouts Of Wrath, The Brentford Chaistore Massacre) I'd be surprised if the locals noticed ANYTHING unusual.

Also, I think the Black Monolith is covering the little blank corner on the map across the lane from the lake, between the lane and the rail line.