Thanks for the insights Mike, well you know ours had a new head 2 years back, been perfect since as it was done by Allans.
I have been looking into it a little and the accepted knowledge now is drive off within 30 seconds. Idling is supposedly one of the slowest forms of warm up (especially diesel) and a time of potential significant wear, cold and less well lubricated. Do read into it for yourself though, I am no expert. I think common sense applies really.. No.1 you don't want to be tearing off down the road on a frosty morn. (with iron filing sparks coming out the exhaust

)
My current approach is head off within 30 seconds and then keep revs under 2,000 or lower in the first minute or so. This can be a little annoying if someone gets behind me but I just pull over on a side road and let them scoot by. No rushing around for me, I take my time and enjoy the ride.
Just done the oil and can always feel that, after 3K miles diesel seems ever so slightly more "gruff" to me. I am sticking with the more regular changes now, but will use more economic oils that are still up to spec.
I did find this and whilst marine specific it is echoed online for cars etc.
https://www.powerandmotoryacht.com/main ... gine-myths
They call me light foot.