Someone mentioned a brakelight switch earlier but I cant find the thread so here is an idea I had that I will give a try. There is a brake light switch that is part of a banjo bolt that will screw straight into the brake master,its available in all the common brake pipe threads and there is a banjo brake pipe adaptor on the good old mini. Bring the two together and there is no need for a tee or seperate switch. those banjos are on quite a lot of leyland cars like sherpas and mini`s. A lot neater and cheaper
Edit. a better picture of one of the banjo`s ,This one is on a range rover
Bob