Hi Simon, welcome, some answers: -
Cam belt, 10 years or 100k, so yes you need to do it. Always do the water pump as well when you are in there.
Run flats make the ride very hard. Most cars have had them replaced and carry a 'get you home' spare.
Plugs I believe are every 10 years as well (not cheap either), I've had my cam belt/water pump done (2002 car), and will do plugs next year :)
Hope this helps.
Paul.