How to select UK pound sign from US keyboard

I have had to use an ancient but quality Northgate OmniKey US keyboard so have had to select the US system keyboard layout so the keys are all correct. Trouble is I can no longer select the sterling pound or euro signs.

In the old days I seem to remember an Alt Gr. sequence but none of these work. In the system settings under Keyboard Hardware and Layout Advanced features however I am spoiled for choice with keyboard options but do not understand what I am doing!!!

For example what does “3rd level of Left Ctrl” mean. If I select a Compose key then what characters do I enter to get the pound and euro. Tried a few options but cannot get it right.

Getting past it I fear. Please can somebody help.

Couldn’t work out 3rd level but did get simple Left Ctrl to work with - L as in £. Now where do I find the Euro and all the other diacritical marks for european languages?

OK folks I have it now.
Spoilt for choice but I have the basics thanks.
Budge

You can find the list of what you can make with the Compose key in your locale in e.g.

/usr/share/X11/locale/en_US.UTF-8/Compose

(of course surf to your locale).

The list is very long, but as you have seen not illogical, like - L for a £, but - l and L- and l - will give the same.

If you’re using the KDE Plasma desktop, open the “System Settings”, in “Hardware” select “Input Devices”, select “Keyboard” and the tab “Layouts”, check “Configure Layouts”, select the keyboard in question, and then press the button “Preview”.

You may find some of the following UTF-8 characters as well (right hand “Alt” key, sometimes with “Shift”): " ⅛ ¼ ½ ⅜ ⅝ ⅞ ™ ± ® © µ " …