Big Bang in boot area going over bumps .shocks renewed 500 miles ago. Spare wheel secured ok. Does feel a bit boatyard at rear.. any thoughts please . Jaguar x type 2002

 

Check the tightness of the bolts going through the lower mount. If that is loose (ie, the 2 tabs that hold the bolt going through the shock are not tight against the shock), it will feel like there is something banging in the back. This was a common issue with Ford Trucks and the fix was to get a larger/longer sleeve that goes inside the rubber mount. In short, what happens is the ears/tabs provide enough resistance that you can't tighten the bolt any more, but leaves the shock loose and over time, the metal sleeve inside the rubber mount becomes oblong. This is what is moving and causing the banging. Back in the day, I had a lathe and I made up a bunch of sleeves for the guys in my truck club. Solved a lot of these issues.

If that is not the case, then you will most likely need to place say some cinder blocks under the rear tires so you can get under the car safely. Then you will need to have someone bounce the rear of the car up and down as you look under the car for parts of the suspension to move around. once you see movement, you will be close to what is the source of your noise.