In my previous update I posted details of my balun design, a trifiliar air-cored transformer.
Here is the resulting balun, a length of 3-core UK mains flex stripped of its outer insulation and wound round a length of plastic water pipe. It'll happily take kilowatts so it's a bit of overkill for my 10mW, however it was exceedingly cheap and quick to make.
I have yet to wire it up, I'll do that when I build the antenna. But if the blue and brown wire are my input/output connections at each end, the green/yellow wires will both be taken back the length of the balun to the other end, and connected to blue at one end and brown at the other.