I would like to change the keyboard layout (since my @ key thinks it's a ",
and vice versa), from whatever it is now, to whatever it should be for the UK
but I don't know how.
Besides setting your preference to English (UK) on the Regional page in
Regional and Language Options, you also need to set that up for your
keyboard. It gets done in the same control panel but on the page tabbed
Languages.
Click the Details button in the text services and input languages section.
Under "Installed services," Select the Keyboard and click the Add button.
Add "English (UK)". After it's added, select it as the default input
language (same page, top portion). OK your way back to the desktop.
Your "global" and input languages now match so your keyboard should start
behaving the way that you expect it to.