900 pounds rig for gaming and rendering (uk)

Hello everyone.

Need some help with my new investment. I need a new pc primarly for gaming and also (very important) rendering and working in all sorts of arhitecture programs (such as AutoCAD, SketchUp, Rihno, ArhiCad...) I need suggestions and tips on what to buy (some builds suggestions would be appreciated). 

Thanks for any help!