wall angle again - could some bright spark help me??

I asked this a while ago and got some great help but now I am actually ready to build the wall some of my original measurements were slightly out so I need some help again. I am going to build a front wall to "skew" my control room around to make use of the splayed internal wall but I can't work out where to put the new wall. Could someone that knows abut these things, or that has a program that can do these calculations let me know. I need actual measurements, angle are no good. The drawing is not to scale but I am building the wall in RED and need to know in actual milimetres to build it out from the left wall to make the splayed angle of these walls the same(or very similar). I would like to leave 200mm on the right wall (as showen) for the stud and insulation etc, its the left wall measurement I need. Thanks again JohnG

here you go :)

Thanks John :)