Stephen, with respect to Jo-Anne, I can't beleive you are dismissing the 307 just becuase of one persons comment! If you always take that approach you will nevere get anything!
I say this becuase my Parents have a 307 HDi 90PS (albeit a hatch version)and they towed my 2002 Lunar Stellar fine and when I upgraded to a considerably heavier 2005 Lunar Clubman they also found it to be fine. Stability wise there are no issues at all, only the lack or power with their version gives a slight dent to what is otherwise an excellent towcar.
See what others have to say before making your decision - maybe the SW is different to the hatch?
Oh, I tow with an Alfa 147 JTD 16V and its AWESOME!