I have my rear suspension with watts linkage now for over 10 years and have really abused it and it has never failed me.
It is a George Petrus product, both the arm and the hub with the watts linkage and it has outboard brakes.My Contemporary came already with the watts linkage support welded on the frame. In my gallery you will see the setup.
Check
http://www.cobraracing.com/index.html for the different rear suspension parts for original jaguar IRS.
It is also very important that when you put your rear suspension back together that you check the rear wheel camber, which should ideally be -1%. To do that I use a digital level and two self made rigs and do it on the lift , even if the car is not level.
I'll be glad to help anyone out on how to do this.