My Dad-in-law has a Nissan Note with a 1.5 dCi, but the closest he's ever come to ecodriving was when he was my passenger. But I'm sure it's hardly different from my 1.6 HDi, so the same engine mods should work.
Grille block. If you are debating how much to cover, then make it openable. Behind the grille the airflow is channeled to the radiator and to the intercooler - each can be independently closed off. As you won't have too many cold starts when it's -20C, then no need for you to block the IC at all.
Prewarming the engine with a 550W coolant heater and a 125W heating pad under the oil pan does wonders if you can organize a place to plug in. I've added insulation to the bonnet, oilpan and intake ducts (turbodiesel engines should be hot, but with cold air intake, both for power and economy). This makes the prewarming more effective, but also keeps the engine from cooling too much when parked for 1-3 hours while running errands.
An engine kill button will let you EOC without reseting the onboard computer. In my case, it keeps the power steering active and (more importantly for Mrs P) does not reset the radio/CD player
The Clio's rear is not Kammback-friendly, but bumping the tyre pressure (try max sidewall minus 10% for starters) equals free MPGs
It is driving technique that gives the most savings (15-30%), but works even better when paired with mods. For example grille blocks keep your engine warm, but efficient driving keeps the blocked engine from overheating.
I'm lucky to have a wife who also drives the speed limit and cares about saving fuel*
And even though she does not engine brake as often, nor does she EOC at all, she can still get figures very close to mine
*) Does not apply to all Significant Others