Thanks for comments from fellow M type owners. Point taken about stop switch position. Present set up was a quick fix to check wiring worked ok. Position isn't actually too bad, being at 'punch' height for right hand, but will be moved down to chip tray level where it can be leant on as Brian says. I will also be moving the on/off/reverse switch which is on the original mounting for the old Dewhurst switch – not a good position being a bit of a stretch and in line with the chuck.
Lathe is very original as regards condition, hence my initial reluctance to drill any additional holes for switches, covers etc. It has been badly repainted at least once though, not quite 50 shades of grey, but a good half dozen, so I am planning a cosmetic makeover with a new coat of machinery enamel. As regards other mods, I will be fitting a spindle thrust bearing as shown on the forums here – it seems like a worthwhile and fairly simple upgrade. A quick change toolpost would be nice, but not essential. I also want to have a go at making a fixed steady for it which would be very useful. If any of this goes ahead, I'll post up in appropriate forum.
The spindle will probably also be coming out to check headstock bearings – it runs very true, but oil runs straight through front bearing and hardly moves through rear one, suggesting a slight adjustment/clean up is needed. Previous owners included a clock repairer and a woodworker, and there was a certain amount of old sawdust hidden in nooks and crannies.