Ok I printed all the X/Z parts and did my upgrade... here is a quick summery:
Geeetech Prusa I3 X 8mm Acrylic
Repetier version 0.9 supplied by Geeetech using Sli3cer
The Parts printed without support perfectly but I had a few small problems more to do with my version Prusa I have.
X-MOTOR_27mm: I had to mount the motor facing backwards as it was "just" touching the frame. Maybe move the motor mount about 5mm more away from the Z Smoothrod for clearance.
X-endstop: The switch supplied with mine was bigger so I re designed my own.
Belt Tensioner: the I3 X has a slight different approach to the "bending Z rod issue". They have 2 Locking collars to reduce this and as you can see in the pics I have retained them.
The only issue I had was the clearance of the belt and the idler bearings. The I3 X used 2 x 624ZZ bearings for the belt (4mm bore 13mm OD 5mm width) I had to find smaller bearings to make it work.
Just a few more pics: