Spell Checking may be working but just not configured:
Start Sylpheed Click on "Configuration" menu Click on "Common Preferences" Click on "Spell Checker" Click on "Enable Spell Checker" Make sure "Default Dictionary" is set to "en_GB" Click on "OK"
Aha! Got it! Thanks for that! Obvious when you know how! Spell Checker is now up and running.
Thanks everyone for all your help!
Ian.