Lol, I have a fan forced oven too. Some of them have a switch to turn the fan on or off, but mine doesn't, so I don't know how they go!

As a rule, I drop the temp by 20 degrees automatically. If a recipe says for 180, then I turn the dial to 160. I don't have an oven thermometer, so I don't really know what it is doing, but that works for me. I have noticed in some recipes that give you all the different temps, that the one for ff is generally 20 degrees under.

Hope that helps!