I seem to be having a problem with the new version of Pages. For one thing it takes ages to load and I cannot find the characters to type the proper symbols for temperature for example rather than typing degC.
There's a neat little toy in macOS to visualise all those pesky keyboard combinations for obscure characters.
Go to System Preferences > Keyboard > Input Sources and click 'Show Input menu in menu bar'. This will put a Union Jack onto the righthand end of your menu bar (if you get a different icon, you have a foreign or special keyboard layout selected).
On the menu bar you can then choose Show Keyboard Viewer. This opens a view of your keyboard, usable with the mouse. If you click one of the modifier keys (eg Option, Shift), the keys change to show the special characters available. You can click the character directly there but I find it most useful for seeing/learning the keyboard combinations.
It works as you say Tony but with one (unimportant) exception. No Union Jack appears in the toolbar. Instead a small symbol which might possibly represent a keyboards appears, and on my iMac (running Monterey) this is to the left of the Bluetooth icon. The Union Jack used to appear in previous versions of MacOS but I am not sure when that changed.
The icon that appears on the menu bar reflects the currently selected keyboard layout (that may or may not match your actual keyboard's markings). On recent versions of macOS* this is a Union Jack for British keyboards.
If you do not have a Union Jack (and you do have a UK keyboard), go to System preferences > Keyboard > Input Sources. In the lefthand column, there will be one or more options. Ensure that 'British' is there (use the '+' to add it if necessary) and select it. The Union Jack will be shown in the Menu Bar.
Some other choices will work just as well as the 'British' setting but others can introduce subtle (or not so subtle) remappings such that keys stop generating what is printed on them (£,#,€ being examples).
*as long as I can remember...certainly Monterey, Big Sur, Catalina.
It seems that you get the Union Jack for the British keyboard (and presumably any other flag for other national keyboards) only if you have more than one keyboard in the 'input sources' column. I always have the Unicode keyboard there too but, as soon as I delete it, my Union Jack goes away even though I wasn't using the Unicode one.
So if you want the Union Jack, add your second favourite keyboard to the list (but don't use it)! I wonder if it's supposed to do that.