You live in Nuneaton right? I live just down the A5 in Burbage 10mins from nuneaton, and they are on an industrial estate just off the A5 before you get to burbage.
they are like full pipes laying on the curved side. and the blocks are 2mins from these.
EDIT: Just remembered, there are a large amount of concrete pipes of various sizes at Earl Shilton Bike Trials Club, its a moto trials club but push bikes are more than welcome there, there are a large amount of tubes, pipes rocks, hills, walls, man made rocks and also a old building with open walls, really nice for riding lots of blocks ect. good place to ride.