[Brekkie]

Sounds like it's new land being built on, not existing property.

If Elstree could house BB elsewhere on site (which they currently can't) though it wouldn't be the worst thing in the world for the house to be bulldozed. I suspect if they were ever forced to move they'd go for building a house on a sound stage if possible rather than building a new house - it seems to be the preferred method now for Big Brother's around the world and gives producers a bit more control over the house itself.