boomer

Bought an A3 2015 last week, I noticed the rear seats were damp to touch, so pulled them out and found a pool of water underneath across the back. From the rust marks it looks like this has been leaking for some time. I cleared out the boot and found more evidence of rainwater penetration in the spare wheel area, also behind both rear light clusters. The car has had a history of rear end damage and been repaired. I have cleared out the drain holes in both sides of the boot behind the rear light clusters, is there anywhere else the water may be getting in from? Any help would be much appreciated.