Thanks for your prompt reply. It's good to hear the background story, and great to hear that support for Band 4 is now a possibility. And as you are aware, enabling this in the Tp-link devices would...

Please consider enabling Band 4 on 5Ghz for TP-Link Wifi extenders and other products, as many other devices (routers, laptops, mobiles) sold in the UK market support Band 4. (aka channels 149-165).