I think it's a drain plug. Wouldn't hurt in twisting it to see what happens, I'm sure someone else knows what it is for sure.
The tray and filter and pump housing is seen here. Freelander 1996-2006 / Fuel & Emission Systems / Fuel Pump - Remote
Item number 12! There about £30. Google the part number.
I'm fairly new to land rover as well so I'm still learning. Good luck.

Thanx a lot for your assistance