A few days ago I noticed a strange sound coming from the back of the car, possibly suspension/wheels.

It can only be heard when I'm in traffic and start driving 0-10 mph, it's an intermittent noise and it sounds like an owl (yeah, the bird). I can't describe this sound in any other way.

Any ideas what it might be?

The car has already got about 20 bits and bobs that need fixing and I am worried it's just another one on the list :(

It could be all sorts of things.

Have a close look at the rear tyres all round, since it might be related to a bulge or a slightly out of round causing one wear bar to be shallower than the others. Also, if your car has rear discs, have a look behind the disc shields, since stones can get stuck under them, and make odd noises when they do.

Brakes would be the first thing to check, does it happen in reverse as well, as could be the famous 'mooing noise' but this is normally the rear pads dragging.

I thought mooing only happened to the vRS.