Have a look in the spare tyre well too - is that full of water. Mine was like a swimming pool in there. If so, there are some bungs to drain it. Common water ingress areas are the hinges and the light clusters. Some members have took off their hatches (you say yours is the Booted saloon? - I'm ***uming the procedures are similar) and cleaned . sealed them up. I just stuck a load of grease on them. The light clusters are worth removing (easy job) and the rubber seals cleaning / revitalising (Autoglym do some suitable products). Most likely with the lights, though, is a small locating pin which goes through a corresponding hole (take them off and you'll see it). The seal seems to be felt or something and most likely perished by now. Throw them, and when refitting the clusters, use some silicone. Have a search round the members site - there's loads of info on this... including my experiences!