Thanks, David.
I have found another possible option. There are aftermarket, adjustable brake proportioning valves that I might be able to use. I will look into them some more over the weekend. Here's some info.
https://www.speedwaymotors.com/the-t...ve-block/29302
As to an MOT, I live in Florida and this state, incredibly, has no mandatory emissions or safety checks!
David.