Sorry Dave but I can't picture what you're talking about.
Most fuel filler door problems reported on here are of being unable to open it.
Can you post a photo of the offending "plastic latch"?
Yeah .. figured a pic might be in order .. will take one tomorrow and post.
The plastic catch is on the end of the fuel door release cable .. the fuel door flap is held closed by that plastic catch .. when you pull the door release cable (beside the drivers seat ) you effectively pull the catch away from the door flap so the flap opens .
In my case the plastic catch is not there now so there is nothing to latch the fuel door flap closed . The latch has disappeared behind the plastic fuel filler surround .
Car is almost 7 years old so well out of warranty now