Thanks Irving - I di think that the kill switch in series with the limits looked funny - effectivley actinas another limit switch and relying on the catches in the switch to keep the power off (dangerous if it failed.) so the second diagram (without the kill switch at present is the next step) - going by the other suggestions in this thread I should use NC contacts. The Home switches look like they are using separate connections with the board numbers mimicing the port outputs.

For the kill switch - would I be OK fitting that to the mains side as a breaker to cut all power to the controller and motors and leave the PC on.

Thanks