The v8 disco 2's have a seperate gearbox Ecu so I'm assuming the td5's do. Trouble is, it's going to need inputs from engine Ecu and probably abs Ecu so unless you can get these inputs to work it probably won't shift. Those inputs may well not come direct from the different ecu'a either they might go via the bcm.
Maybe try getting wiring diagrams and studying how it is connected? Or buy a disco and find the Ecu and remove wires from the trans Ecu and see if it still shifts?
I've recently bought Compushift from Dave for running a p38 box in my winch challenge buggy and its a very smart looking setup (not fully fitted yet) it's a lot of money but for a near enough plug and play situation it's not bad value,