Which studio is it?

BEcause in BBUSA didn't they have a proper front door and now the studio is in the studio.

So where was/is it filmed in the CBS Lot?

CBS Studio city next to the freewayyyyyyyyyy, sort northeast on the lot, u can see the garden on googleearthy

I can't remember, but I don't think they have ever had a real front of the house (i.e. on the outside) have they?

See here for a direct link to where it is on Googlemaps.

Big Brother 1 did.

You can see the Enterence, The Black Wall is Obviously hiding The Production Offices

You're right, it was more like our BB1.

As demonstrated on youtube.

But by BB2, it was in a studio. [YouTube again]

LOL, great minds.