Hi Geoff sorry for not coming back quicker as i have been snowed under rebuilding my workshop and other things so my build had stalled quite a bit. On X and Y i went for 16 and 24 HTD5 15mm pulleys and belt, as for the Z i kept the existing rack and pinion and added a plate with a bearing fitted. To this i a have 72 toothed pulley with a 16 on the motor. As for the screws if i could do again i would have just gone 16mm instead of the 20's as it would have been less hassle and im sure up for the job. I did consider mounting a screw for the Z in the base mounting the ballscrew to the base of the column but would have been quite a big job with conventional tools. I might still do this when the machine is up and running as i can make the parts on it. I'm using the similar motors to you and they should be fine. Hope this helps a bit?

Paul