When BB moved to Channel 5 the contract for the surrounding studios that housed BB's production base and supplied studio space for BBLB, BBBM, and the eviction shows could not be renewed... Channel 5 instead built a temporary production village in the area surround the house and the old outdoor stage was enclosed and converted to studio space... At this point the facilities are there so unless the council decides not to renew planning permissions the production village is here to stay... The green area surrounding the house known as the mound is rumored for over a decade now to be a part of an expansion of Elstree studios which is probably the main reason the house structure has never really gone through any major revamps...
The structure itself is actually quiet spacious but hasn't really been used to its full potential since the first series after the move... I'll post a link to the BB3 launch and you'll see in the house tour how much a difference that house is compared to other designs... The decision was made for BB5 in 2004 to drastically reduce the size of the house including dropping the height of the ceilings and raising the floors to give the house a more claustrophobic feel which in turn was intended to create conflict and essentially drive the HM's mad... Davina gives a decent explanation of the changes that were made to the BB5 house in her house tour so I'll also post a link for that as well... While there have been attempts to increase the space used within the house things like secret rooms, task areas, and other house features that have worked their way in to the design over the years eat up quite a bit of space and has decreased efficient use of the space... There's also the fact that production still seem be under the impression that a smaller house leads to increased conflict and the raised floors and lowered ceilings have remained...
