Water Leak into Boot
There has been a lot of mention on the web of leaks into the boot and the usual cause is the failure of the light cluster seal. These are easy to replace, but be aware that the seals come in two different thicknesses, so make sure you get the thicker one. However, my problem was a little different. I had replaced the seals and still had rainwater getting in. In theory, the thicker seal is supposed to guarantee that an effective watertight seal is created all round, allowing for any misshapen body sections.
My next step was to smear grease onto both sides of the seal before re-fitting the light cluster, but this failed as well.
Becoming more and more suspicious that the was either a deformity of the body panel surround the light cluster, or that somewhere there was a section of body panel sealant that was failing, close examination revealed the cause.
Using a mirror to look at the underside inner face of the body panel, showed a section of rust
Having seen that, it was then just possible to see the fine gap between the panel sections where the ingress was occurring.
An application of silicon sealant to the outside of the gap, and pushed into the gap using my finger, then over-sealed again, cured the leak.