Hello, Andrew Glendenning1
Welcome to Microsoft Community.
The keyboard layout for English US and English UK is not the same. If you want to type @ in a UK English keyboard, you need to hold down the Shift key and then press the single quote key, as shown in the following image:
United Kingdom Keyboard - Globalization | Microsoft Learn
United Kingdom Extended Keyboard - Globalization | Microsoft Learn
The way to enter @ on UK Keyboard and UK extended keyboard is the same. Just hold down the Shift key and then press the single quote key.
Let me know if you have any other concerns.
Best regards
Yuhao Li
Microsoft Community Technical Support