Just done a quick test using Google Photos. Result! I used the Original Size option on the Google Photos app on the V30 as that's important to me, but I'm limited to 13GB in the cloud that is free, which should be more than enough.
Getting them onto my Mac was simply a matter of logging into Google Photos via Safari and downloading each of the pictures that I wanted via the web interface. There's probably a method of tagging multiple photos and downloading all of them at once, but the current functionality is sufficient for me. The bonus is that I can disable the Bluetooth sharing on my Mac again.
A big thanks to
@VI001101106 for the suggestion (and to anyone else who suggested Google Photos. There's no faffing about with apps on my iMac, cables, etc.