hi Dewi, there is actually a special rice (called pudding rice) which you need to use for this dish. the rice is available from most supermarkets (I know the def. sell it in Tesco's and Sainsbury's).
You should definitely use pudding rice if possible. It is lovely and creamy if you use evaporated milk instead of ordinary and don't forget to put in the knobs of butter and grate loads of nutmeg on it before you cook it. I love the skin best of all.