When I open the boot, it’s got a few drops of rain water on the right hand side in this little hole bit by the light, but I can’t work out where from..... I can’t see how any rain water can be getting in there! When I move the seat down, where it dips in, is also a bit wet, and then goes to the floor. Along the edge of the boot, right along the right hand side is wet!

I had the rear vents resealed a year ago, no water is in the spare wheel area, that’s dry? 

even my pushchair in the boot has now gone mouldy because it’s damp!! I poured a jug of water over the lights and looked underneath but couldn’t see any water dripping in so I’m unsure? 
 

can anyone help advise on what to do? I know rear vents to be resealed is common but I only had it done a year ago!!! 
 

thank you! 
 

It is a 12 plate mk3 focus. 

Pull off the plastic inside the top of the tailgate behind the spoiler they should pop off and see if the water has leaked through there. 

Pouring water on the lights may not be enough, you might have to use a hose pipe on them to get them to leak. I have a leak in the same place, and I often see drops of water running down the carpet under the back light area on the drivers side. I know for a fact that mine leaks on the screws that secure the light. As Focue says, check the rear spoiler as well.