@Hippo A five minute tick over is easier than driving it about, so I shall give it a go next time, probably March.
Mike
The 5 minutes at tick over from cold is fine for the V6. The engine coolant will actually heat the box fluid via the oil cooler.
The TD4 is much slower to warm up. This requires a longer warm up time at idle or some help. To warm the TD4's box fluid. Let the engine idle with the box in D for a minute or so (brakes on). This will warm the box much faster. It's important to measure the temperature though. I use an infrared thermometer aimed at the drain bolt.