I have this idea which I have done before, but cannot work out how. That is set up a keyboard shortcut to run a script. Can it be done?

Yes, it can be done: UE > Advanced > All Scripts

This brings up the Scripts dialog box. Select the Hotkey field for the script of interest. This field becomes editable with visible cursor.
Enter your key. Mouse click away from the field. (Not sure pressing enter here would work.) Voila.

Now in 5 years time when I have forgotten I can look up my own post

Script with hotkey assigned in scripts list.