As daft as it sounds, check that the spare wheel is tightly bolted. I've taken mine out completely, but the bolt holding it in causes some stupid rattles and squeaks when it's loose. Don't turn the car down if that's all it is!

Loads of Essex members might be able to help you out, and listen to it with you. There are lots of owners around your area.

 

Hellafix

 

I'm essex!

PM if you want a hand!