I have one of these - http://www.victoriasbasement.com.au/Product/Details/75766 - which I bought recently. Its an enamelled cast iron pan. I've been seasoning it by rubbing it down in oil and putting it in the oven. The seasoning doesn't seem to last very long though. Should I not be seasoning it because its enamelled? If so, should I try and get a non-enamelled cast iron pan if I want something with better non stick properties?
You don't need to season an enameled pot. The enamel serves much of the same purpose as building up a layer of seasoning.
Although the enamel won't ever be quite as slick as seasoned cast iron, it protects the vessel from rust, makes food less likely to stick (with a little help from some oil), and easier to clean up afterwards.