The structure you can see in the picture is a huge covered water tank that warner brothers built to film scenes for moby dick the water was drained from it and the bb house built on top of it (well actually inside it). The shape of the bb compound (trapezium) is because that was the shape of the concrete tank.
Parts of dam busters were filmed there too.
The house is still there if/when it is removed its planned the water tank would still be usable for any future needs.
The first couple of bb series at elstree the housemates apparently complained a lot about the amount of flies and insects etc. this was because although the pool was drained there was still thought to be stagnent standing water under the floor of the house and the house being relocated is also why after a couple of attempts they also had to give up on having a real lawn.
The pool/bb house location
