I am unable to copy and paste in Illustrator.
Shapes don't copy at all. Text copies the wording but sets the type and colour to standard Myriad and black?
I think in the process of doing some short cut I have pressed a load of keys with my chubby fingers and now it doesn't work.
Any ideas how to change it back?
Try resetting the preferences ,
hold Cmd-Opt-Ctrl-Shift when restarting AI on a Mac or Alt-Crtl-Shift on a PC to reset the preferences to the factory defaults.
Please mention your OS and Illustartor version
You may have a look at the next step(s) here:
1) Close down Illy and open again;
2) Restart the computer;
3) Close down Illy and press Ctrl+Alt+Shift/Cmd+Option+Shift during startup;
This is where you are now.
4) Move the folder with Illy closed;
5) Look through and try out the relevant among the Other options;
Even more seriously, you may:
6) Uninstall, run the Cleaner Tool, and reinstall.