Yup, this is the garden although, once the programme decamped to Manchester they obviously filled-in, and turfed-over, the iconic Italian Sunken Garden (as well as removed the Petra statue and all the other gubbins). I haven't seen the show since it moved to Salford Quays so I have no idea whether they were transplanted to their new home. I hope so.
The area of darker grass was where Percy Thrower's pride and joy (and occasional target for vandals) was located.
The garden was an area of land at the base of the restaurant block. This pic was snapped from the balcony of the (by-that-point abandoned) dining area. The grassland, on the other side of the wall, at the top of the picture, is the edge of Hammersmith Park at the back of the Centre.
The blue construction in the foreground was a permanent camera platform for filming.
When I started working at TVC, the BP garden was one of those icons that HAD to be sought out in the first few days of exploring. Surprisingly, staff were free to use it when filming wasn't taking place. There was a gate, far to the left of this picture, to control access.
Post-Broom Cupboard, CBBC had a studio (again to the left of this picture) which looked out on the garden. I have some exterior snaps of that which I'll post in future.
It was - predictably - smaller than it looked on TV... but no less iconic.