Remap tilde key to top left on a UK MacBook rather than bottom left. Place in: ~/Library/LaunchAgents/local.remap-tilde.plist and run: launchctl load ~/Library/LaunchAgents/local.remap-tilde.plist

local.remap-tilde.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC -//Apple Computer//DTD PLIST 1.0//EN http://www.apple.com/DTDs/PropertyList-1.0.dtd >
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>local.remap-tilde</string>
    <key>ProgramArguments</key>
    <array>
        <string>/usr/bin/hidutil</string>
        <string>property</string>
        <string>--set</string>
        <string>{"UserKeyMapping": [{"HIDKeyboardModifierMappingSrc": 0x700000064, "HIDKeyboardModifierMappingDst": 0x700000035}, {"HIDKeyboardModifierMappingSrc": 0x700000035, "HIDKeyboardModifierMappingDst": 0x700000064}]}</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
    <key>KeepAlive</key>
    <false/>
    <key>AbandonProcessGroup</key>
    <true/>
</dict>
</plist>