Broadband router is giving false messages via its LEDs, claims no 2.4 GHz networks are being supplied. But I can log into the three networs it's spitting out in that frequency range. Plus, looking at the actual settings via Safari shows all is OK. I used a Mac app called WiFi Analyser to check which channels mine are using.
I'm the only local user putting out a 5 GHz signal so there's no interference there. My ISP connections are the only 2.4 GHz ones on channel 11, my AirPort Express has by far the strongest signal on channel 6. Every other silly bugger is on channel 1.
Losers.