Nigel, Princess Auto sells a twist knob that'll work fine: I had one set up in my petrol Montero, and can show you how I did it if you want? But how come your batteries are not running together for startup? Did you add one, or did it come with two? The OE config runs em together, acting like one big battery...

Neo, my glowplugs are greentop too. I think they're the "fast cycle" or some such term.

1991 HZJ77, 1999 KZJ90, 1999 UZJ100, 1992 M101CDN2
https://www.thegearheadproject.com/category/jdm-journeys/