Managed to find an electric step off a mini-bus at a local scrap yard that fits great under the side door. It was minus a control box, but I rigged up my own using two relays wired to the step's micro-switches.
I rigged up my own mounting brackets underneath. The front ones were quite easy as there was some metal box-section frame for the sliding door. The back fixing needed a length of my own box-section strapped between the chassis framework. No need now to carry round the stepping stool that I've been lifting in & out
Its going to need a revisit to finish, as I got rained-off. The step is presently working in a semi-automatic mode via a switch inside, but needs a feed running to the sliding door 'light switch' plunger that will make it activate with the opening/closing of the door.
Changed the switch labels on the main control panel to white on black
Trimmed around the over-cab doors a few weeks back, but don't think I posted any pics...