My original plug and socket (5pin) on a new ST 2000 became rusty,was like a Bulgin but clearly not a Bulgin,so replaced with a much more cleanable two pin Bulgin with plated contacts,before it was repaired under warranty,having failed in heavy rain in the last week of the extended 3 yr cover.No quibble .Betcha lose any warranty if you have to change the plug. Gotcha by the short n curlies. Do check first.
I believe current cables are shielded, and the shield goes to the 3rd connector.I could be wrong, but seem to remember that although the plug and socket are 3-pole, the power cable between control unit and drive is only 2-pole. So if replacing with other connectors, 2-pole should be fine.