The Cardiff Bay Development Corporation had several SDOs granted for the Cardiff Bay regeneration project. The project still took 13 years. It's difficult to put an exact time frame in how long planning took, even with the SDOs, because of overlapping projects, but it's a decent comparison.
In-fact, the Wiki entry on Cardiff Bay Development Corporation reinforces the efficacy of the SDO - for this project at least. The Universal UK project is just a fraction of the size and should be a breeze in comparison [he says
From Wiki
During the CBDC's lifetime [April 1987 to March 2000] 14,000,000 square feet (1,300,000 m2) of non-housing development and 5,780 housing units were built. Around 31,000 new jobs were created and some £1.8 billion of private finance was invested.
The corporation was established as part of an initiative by the future Deputy Prime Minister, Michael Heseltine, in April 1987
The corporation was dissolved on 31 March 2000.
Cardiff Bay Development Corporation