I have a 2005 Ford Focus from new and have never used the cigarette lighter as I don't smoke. I have just got a sat nav and have found that the cigarette lighter does not work. Anyone know how to get it to work?

Most likely a fuse.

Use a test light or multimeter to test all under dash and under hood fuses:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post252145