Well got fed up with it so re-installed mach and now seems to be working better. What I do is zero x y for the job, jog the tool down to the sensor till the led is lit, zero z, then type in 45mm in to the z dro and all works, it's a right pain having to do this for eevry tool change but at least I can cut now. Would love to get it working the way DSP did JUst press a button for auto z and tool height and the same for each tool change, tried some scripts but none of them seem to work too well, will have to try that 2010 screen set, will that work with only 1 tool sensor. I really would have thought that mach3 would have included a script for that as they have an auto tool height button but I suspect it is aimed at more experienced users who can erite scripts, looks like I have something new to learn!!
Thanks for you help