Hi firstly as a scarlets fan I would have to say 9-3 not many teams can do that. As for the paint as others have said all white paint will yellow in time. The best way to keep it white is to let as much light get to it as possible. I am old school and like oil paints but waterbased gloss does stay whiter longer and eggshell stays white about the best but as rowanwitch says it is not the easiest thing to keep clean. Also I am not a fan of Once or any one coat paint and think that you will get a better longer lasting finish with one or two undercoats plus a finish coat. If you just put on a gloss white coat on to yellow or discoloured paint it will not stay white for very long, the other colour will bleed through. So by using the undercoat before glossing you are sealing in the old before putting on new which should give a longer lasting finish. Which means you don't need to do it so often.