Having had many leaks, oil, coolant and diesel on my TD5 when first purchased I know your pain. By far the best way of tracking is a UV detection kit, you can get for oil and water. Give the offending area a really good clean, add the UV trace and check with UV torch.
As Thomas mentions, I found a fuel leak from the fuel regulator at back of engine, real pain to get to. Oil leaks from the back of the rocket cover, and the main one was the crank seal, big job. Coolant was also leaking as the water pump was gummed up with calcium as someone had been using tap water in the coolant.
Below is a link to the type of trace kit, I have no association with this company, I just pulled from the tinterweb.
You do not own your Land Rover, you just maintain it for future generations.