Advice required

My discovery 2 (2001), which I've only had for 6 months now, has a very audible noise pick-up between 55 and 60 mph. This seems to be coming from the engine/transmission area beneath the front seats, but could be further away. When beyond 60 mph the noise decreases. This is noticible both on acceleration and deceleration.
Does anyone have any experience of something similar and any suggestion as to what could be the root cause of this. I'm thinking prop-shaft but not sure if a simple UJ issue or actual shaft. Possibly transmission?
Any advce would be greatly appreciated as I don't want to take it to the dealer and have them tell me there's a whole lot of stuff wrong when it could be one isolated problem.
Cheers

could be prop if you can see if there is any play on the prop the UJ had gone on mine but that was more of a clank when you first put it in to drive or reverse,

there is always the thrust bearing wearing someone will be along sone that'll know

manuel or Auto

Thanks Rob - Auto box.

No worries mate
Might be worth posting in the Discovery section they are all probley down there the ones that'll know