I have had an Aygo for the last year or so now. I noticed water in the spare wheel well, but used to account for it as entering during a wash. However, when it became clear that this was not the case I tried to find the source of the leak. In my case this was as follows: Water flows around the rear glass seal in the small channel formed between the seal and the rest of the body. This should then overflow and spill out with no harm done. However inspection of the rear lights shows a small gap between the light and the body, and water can be seen to flow into this gap. On trying to pour water into this gap, I could see that water enters the boot from under the carpetting on the left hand side. On removing the carpetting and piece of plastic around the rear left seatbelt (this is described in the owner's manual as the procedure to change the rear lightbulbs), one can see much more clearly what is going on. The light is fixed to the body with only one screw and a clip, containing also the electrical connection. This electrical connection is surrounded by a foam seal, which when the light is tightened to the body should seal any water from entering. However, this is not he case and water can be seen to seep in through this seal and into the car. How does it get to the rear footwell one may ask? Well, following the water from the light, one can see that it flows along the boot floor, and the little river then splits into two: one flows down into the spare wheel well, while the rest continues flowing towards the rear seats and flows down into the footwell through the small gap between the seats and the wheel arch. My solution was to fix some foam tape to the top of the light housing, such that when fixed, it prevented water from coming into the connection seal. When tested it worked, but lately I have seen that water has been coming in once again. I don't know if it is due to a new leak or whether my patch has failed. Anyway, i phoned the local Toyota dealer (in Malta) and he replied that he knows of the problem as they have had another two cases and know how to fix it. So it's off to the garage on Thursday. I'll let you known how this ends up. This has been my personal experience, so I don't know if all Aygos are having the same problem as this seems simple enough to find, and can't understand why Toyota UK can't seem to find a simple leak if it is in the same location as this. On the whole very please with my Aygo and my dealer as well.