As far as I was aware (been heavily invested in the sale of the Clifton site). The west car park was put up for sale around 14m and had very little interest. There was muted offers of far less, pre planning, but BZG proceeded to obtain planning themselves to mean planning was secured on the site for a number of properties which would increase the purchase value.
As far as I understood, after planning was secured, a buyer came forward and a deal was agreed, but the figure wasn't as high as the 14m initially wanted or the 12m being branded about. From what I read, and was told, The Hill Group secured the purchase for around 10m, after the approved planning had to include 20% of the site to be "affordable" housing. As a luxury 5 star housebuilder, The Hill Group would not normally build Affordable Housing, so for them to purchase the agreed fee was reportedly in and around 10m.
From what I understand, the funds secure Phase One of the zoos build as highlighted by Charles above.
The sale of the main BZG site is proving much more problematic, with planning secured, they had hoped to be able to sell, but there appears to be little interest and local objections have put off some big powerhouses, and very few developers wish to develop the land to the way the zoo have secured the plans. Late last year the government have backed the plans, but the area is a long way off sold, and it is only the sale of this area for a rumoured 40m+ which can fund the 10 year plan of BZP.
Whilst phase one is secure, I don't think it is unreasonable for people to question, the future build and expansion, if the main site continues to remain unsold, having to be maintained at a reasonable cost and generating no income.
Phase one is definitely exciting, but there is a rumoured 4/5 phases before this can be a modern day top zoo, and a timescale of up to 2035 was given. But without the sale of the main zoo site, and other funding, no one can be sure just how much of this plan will ever come to fruition.