There are some very experienced Rover folks on here but if your description of symptoms is unclear, it's not going to be very easy to provide any help at all. The LR is a complex beast and the noises could be coming from anywhere as you didn't say where it appeared to come from (location) and whether it appears speed/revs/steering direction related. We've got engine, transmission, front and rear differential, transfer case, prop shaft(s), CV joints, wheel bearings....you get the picture
Go to your doctor and say I have a pain, can you fix it and see what reaction you get.
I'm no expert mechanic but if the dealer selling me the car told me that the "annoying thumping sound" was normal then either I need my head testing or he's totally correct....I'd check the two month warranty and see if it was written in disappearing ink....