Getting into this DCC lark, I thought I'd have a go at an old Hornby rat with the old Ringfield motor. I found the hidden pin that connected the pick up directly to the motor and separated that. I haven't sorted out alternative pick up yet but have tested the rest of the workings by temporarily connecting the black and red wires to the track, grey and orange connected to the brushes and it's running well. Looks a bit of an untidy mess but now I know it's working I'll tidy everything up.

I'm considering whether to solder the black wire directly to the hidden pin or to make some pick ups for that side and retain the non powered pick up for the other side.