Ford Focus MK1 - Where is my boot leak coming from? 

Those rubber bolts are for fixed the strange roof rack for our 3 door Focus. This is a usual rusty point, just to cover that point with a bit of paint spray is good. If that point leak to much the spare wheel site will be full of water. Sorry if my english is not good.

Also the boot seal can be an entry point. Where it meets at the bottom there is often a small gap which is enough to cause water ingress.

I just pulled the entire rear of my hatch apart looking for a leak and have found the plastic triangle trim panel at the back of the rear side glass to be leaking. Just another spot to check. Cheers. Edit: this is only on the 3dr models. Silicone around holes and plastic clips should fix it.

Those grommets you mention. Here on the mk1 US cars, Ford inserted a threaded nut in there to accept the roof rack specifically designed for our special edition Kona trim package cars. I myself have installed one on my own car.

Life saver my car suffers from bad leaks and have been looking in depth to find reasons and couldn't find out till now

At my wits end now with my boot leak. Haven't had chance yet to remove the rear arch liners and work on that area but I have bought new vents. On the left I sprayed a load of Dynax first then double sealed the new vent in. On the right I couldn't renew the vent as a cable is running through it for the tow bar electrics but again I dynaxed that area and sealed the vent. The tailgate hinge bolts were all tight and dry in the roof lining. No sign of water in the electrics or rubber sleeve. I siliconed the seams and rubber screws as shown in this video. When I removed the lights the rubber seals were completely dry. I drove to work last night in the pouring rain and when I checked all seemed ok. When I finished work after much more heavy rain the left side by the vent was dry and the right was soaking. As the car hadn't moved during my shift I can only assume it's not coming from the arches with water kicking up

How can I tell which of these is the problem please? I bought my car recently from a friend who explained the damp in the back asbhes left it open in a downpour. Had never had issues before. The car is now leaking badly, I was away this weekend and noticed dampness on the left hand side od the boot carpet, the footwells had filled with water by the time I got back, serious standing water. I've never done this kind of repair before, can you reccomend any how to guides please? Is this something a garage could do for me and if so how much would they charge? Thanks for your help.