Thanks. Yes, I'm using WiFi currently. Maybe I can try using a separate WiFi dongle, and see if that improves the Bluetooth? I wouldn't have thought to do that. I've got a spare one I can try.
I found it was pretty hard to buy long range Bluetooth LE dongles anywhere.
I spent a while looking into it and found a couple of things on eBay, but there's no way of knowing how much, if any improvement I'll see.
I guess I'll try the separate Wifi dongle, and if that doesn't work I'll probably just get the one you're selling. Thanks.