Omega fuel tank woes ? - robert

For some time now I've had a rattle from the back of my MV6 saloon. I've tried everything to pin it down - to no avail. This afternoon I wanted to take a good look @ the wear on my rear tyres and lay down under the rear of the car. In the process I knocked the bottom of the tank and hey presto - what a noise.

So, question - is there anything inside the tank that could not be as secure as it should be - is it replaceble or do I need a new tank? Is this a red herring and do all tanks do this if thumped in the middle of the tank - I suppose I need to find another Omega, lay underneath it and do the thump test!

Advice comments please.

Regards ............ Robert