If that doesn't help, you'll probably need to uninstall the sound and touchpad drivers. Restarting your laptop should then see them reinstalled automatically.
Scroll down to 'To uninstall your audio driver' and follow the instructions, including restarting your laptop to get the driver to automatically reinstall itself.
The technique for the touchpad driver is the same.
All sorted this morning. I run updates to touchpad driver which released whatever was stuck - not only the touchpad but the keyboard function keys and the on screen audio controls. All working again now.
Thanks for your help.