Ovens - Many/most ovens are fan ovens (aka convection) and temperatures are shown in Celsius. If you have your temperature in Farenheit, to make things easy in converting to Celsius, you could generally halve the Farenheit temperature. It's not exact but it works well for many. Also, with fan ovens you must either reduce the C temperature by 20-25 degrees or reduce the cooking time by 10-15 minutes. Most foods have instructions for both types of ovens on their packaging. Gas cookers are set by "Gas Mark".