Sorted this out. Wiring is as my diagram, the black output from the controller isn’t connected , it’s capped off to make it safe. I read this post again https://forum.mx5oc.co.uk/t/cheap-daytime-running-lights-drl-fitting-on-nc/115978 and whilst a 5 pin relay is being used instead, noticed that the other output was made safe as it would be live when the headlamps turned on, as will be the case for my controller.
I’ve wired my DRLs to go off rather than dim for now. I’m just glad to have worked out the wiring so I can put the front back on the car.
I’ve ordered a relay in anticipation of the controller failing, and may trying the dimming option then, although I try think that the legislation is that the DRLs go off, not dim.
PS I have removed the gold resistors from the DRLs as I have modified the flasher unit as in https://forum.miata.net/vb/showthread.php?t=629313