https://www.ebay.co.uk/itm/Apple-MacBook-Air-13-A1466-2013-2014-2015-2017-WiFi-Airport-Bluetooth-Card/253268775818
https://www.amazon.co.uk/gp/product/B01JR5TGNK/ (powerday®BCM94360CS2/BCM943224PCIEBT2 Card To NGFF(M.2) Key A/E Adapter For Mac OS)
Reporting back on my purchase of the above two dongles. Both work fine with OSX and Windows yay. The bluetooth dongle was plug n play on both systems. The wifi needed OSX drivers downloading, not from their website, but from a link given on their Amazon page, bit odd.
Wifi works fine in OSX with my 802.11ac router. However in Windows it slowed to a crawl. I had to have it drop back to my 802.11n network which I'm trying to keep clear, but it ran reasonably fast on that.
Two annoyances: bluetooth doesn't work with Clover for selecting which OS to boot, but I can live with that for now. Second annoyance my Apple Wireless Keyboard doesn't bloody work with Windows, which I had expected it to to. Any help on that?