I couldn't be arsed to tweek Sam so I replaced the rear brake with another and it still binding less, but I has re-greased the cable and sprayed some GT into the levers and think the washers were still new and tight on the dual handles, but I have full stopping power on the little bike now!
Derailer and chain next, but waiting for a Park tool chain splitter to arrive.
So start with smallest gear cog first?