Hmmm well I've tried but I just cant get to grips with Fusion360. I tried one called LISA which was ok drawing wise but the actual FEA never worked.

As I see it the gantry and Z are like a T in cross section, which means its a simple bending calculation. I'm getting around 0.025mm deflection at 1 meter with 200x100x8 seperated 400mm center to center.

Think I'm going to have to scale down my plans though. I will have to find a cheaper alternative to what i'm looking at the moment, maybe just wait for stuff to come up on ebay. Currently I'm pricing it from Zapp Automation for ballscrew related stuff and cnc4you.co.uk for the rails/carriages.
£110 Ballscrew support fixed end
£36 Ballscrew support floating end
£88 Ballscrew
£132 Ballnut
£37 Hiwin 25 Carriage
£37 Hiwin 25 Carriage
£108 Hiwin 25 Rail
£40 Motor
£10 DIY motor driver
Thats about £600 per screw. I need 6 screws for the basic XYZ table thats £3600. +2 for the lathe tailstock £4800. +4 for the moveable bed £7200.

So now I have to decide whether it would be best to get an old bridgeport for around £2000.