I subsequently have to set my Mac keyboard layout to PC to fix backticks and remove that key that is never used, and rely on my touch typing. It does also mean that no one will ever try to type on my laptop.
Eventually I settled on Karabiner Elements, an app that lets you create a simple modification specifically to target the Mac internal keyboard where you can map `non_us_backslash` (that strange unused key) to `grave_accent_and_tilde` which fixes this.
(This may not translate well for USians; Quake disregarded keymaps, so the console wasn't actually on ~, but on "the key that would be labelled ~ in the US". On UK-PC, that's backtick, on Uk-Mac, that's §.)
Back on Mac now with British PC and it's much less frustrating to use the keyboard. Plenty of other frustrations instead. I'd prefer to be on Linux but the hardware is just too good.