My router wouldn't go into 40Mhz bonded channel mode due to neighbouring networks on channels 1,6 and 11. I tried to get the neighbouring AP on 6 to change channel by temporarily running APs on 5 and 7 but that didnt work. As I wanted to use a channel 7+11 bond. 'sharing' a channel with another AP works, being on an overlapping channel should/does not.

The module did connect at 72.2Mbps in 20Mhz mode which is better than the ESP8266 board did (though the ESP board should in theory support that) and managed throughput in the region of 40Mbps, no improvement over the ESP8266 module.

I wanted an AC1750 router anyway and my new router happens to have a naughty '40Mhz only' mode. This allowed the module to connect at 150Mbps but didn't help with the throughput as about twice as many packets were dropped as not.

I can't say for sure if the dropped packets are from interference due to forcing 40Mhz mode, the RF layout of my board or the driver. I've tried a few drivers (e.g CHIP one) but the hadess one appears to be the most stable.I've tried 4.1 and 4.4.1 Pi kernels.

But what this has really told me is I need to find a dual band 5Ghz chipset and dual band antenna. Let me know if you have a better idea than a U.FL connector and something like this.