I work at a Holden dealer as a technician,and have for over 15 years.
Don't tar us all with the same brush OK.
I have successfully re-glued these for customers in the past with great results.
Remove the fuel door hinge (3 screws) and reglue with super glue,use a good quality brand like Loc-Tite or Wurth for best results.
It is very important not to use too much glue and also to align it perfectly,then hold it there while it sets completely(about 30 to 40 seconds).
What I do next is get some of that thick clear plastic like they use for laminating posters etc.
Cut some small squares out of it and bend them into 90 degree angles.
These are then glued across the broken joint ie. one side on fuel door,other side on hinge if you know what I mean.
You must fully cover the area of the laminate with glue and squeeze out all the air so you get a really strong joint.Don't get any on you fingers,because that's what this stuff sticks best

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If you can't manage to do the above sucessfully,get some of this stuff
Q-Bond Adhesives | Blackwoods places like Repco sell it and it really is a good product.I've used it on all sorts of jobs and it really is magic stuff.
Hope this helps.