I had the same problem Paul, my car could not be tested at the MOT station because fuel was leaking from the fuel filter. It wasn't much but it was constant and you could clearly smell it from inside the car.
After having a fiddle with the fuel filter it became clear, this was my problem because as soon I adjusted it and started the car, fuel would literally pour out. No amount of readjusting would stop it from leaking, so I went to the dealer and ordered a new filter. Took 20 mins to fit and voila, jobs a good'un. No more leaks or smell.
If your fuel filter is ******** it will be hissing slightly because it is clogged up. Change it asap because it will be putting more stress on your fuel pump, and if that goes you're proper ******.