Petrol leak?
Are you loosing fuel when not using the car? If you park on a concreate drive/garage you might not notice fuel lost as it quickly be absorbed by the concreate or evaporate. But you'll smell it. Do you smell it before you start the engine?
I had this on my old mini, loosing fuel but couldn't find a leak, but on checking the fuel lines closely I soon found a small section of porous pipe which after draining the tank was quickly cut out and replaced.
First thing I'd check is fuel filter and make sure its ok and not leaking, then check petrol line as best you can from tank to engine bay.
