cheers guys
the rattle to me sounds like the heat shield but Fiat have apparently investigated that and the exhaust and passed
only owned my qubo for about three months and iv had more trouble with this than my ten year old punto
what you need to do is locate where the noise is coming from, you say it sounds like your dragging a tin can round but then say like plastic bottle.
steps to take:
get a urchin or small person to sit ion the boot while you drive , if its coming from rear of car they will be able to see which side it is or if its just at the back empty the spare wheel well take out the spare and all the tools makes a nice seat to sit in lol ( well thats asuming you have one )
if it is coming from one side remove the inner panel or carpet and with a mirror and torch see if you can see down all the openings at that side (inside the body panels) this is because stuff could have fallen down there, maybe only a screw or similar but it could be rattleing against the side panel, if you can see anything but cant get it out either get a tin of spray glue or spray underseal and spray it, when it sets it wont be able to move anymore then see if the noise has gone.
make sure you drive it without all spare wheel stuff in as it may be the tool kit or jack thats rattleing.
alternatly take to a friendly garage and see if he will test drive it and see what it is, if he finds the fault bung him £20 take back to fiat and tell them what it is.
you didnt say how old the car was if its still under warrenty ring or email fiat uk direct and tell them your issues, they are pretty good at sorting them out, remember your local main dealer is just a garage that has a franchise to sell fiat cars they are not FIAT UK.
hope this gives you ideas