Hi Mickey,
If the dohnut part you describe is in the middle between both propshafts then its the centre coupling. They cost around £600 to buy and are very easy to fit, that said I want to ask you a couple of questions first to fully diagnose the prob. Are you experiencing any loud hum or whine from the front wheels as well? Is the car a bit sluggish and almost feels like its pushing more weight? If so then the propshaft bearings will almost certainly have gone as well. It happened to mine recently. I suggest using the internet to search for used propshaft assembly, that will give you the 2 props, centre coupling, all bearings and new diff coupling bearings as well, usually for about £300 and it's very simple to fit that lot, 4 bolts in the middle, 4 bolts at each end. Takes about an hour. Just so you know if you buy this lot from Landrover it will cost you £1378 for the parts alone, christ knows what they would charge to fit it!
Hope that helps