Apologies if covered before but couldn't find.
Is slow warm-up a characteristic of the engine or is it possible that my rad stat is stuck open? Reckon on 4 to 5 miles before anywhere near normal temperature.

normal I would say especially with a diesel which take longer than petrols to warm up.

mine takes 5-10 min from a cold start

Thanks - comparing it to FL1 though it is quite a lot slower but that may be just down to colder weather (bought in November)

As modern engines get more efficient less heat is produced per unit of fuel so engine takes longer to warm-up. Oddly this makes the engine less efficient for short trips as the engine uses more fuel when cold. peak mpg can only be achieved at normal engine temp.
So the idea of an electric engine heater in the garage makes more and more sense.with the added benefit of the heater blowing warm air at you as soon as you set off. For those of us who use the car at the same time everyday - work/school runs etc - this could be on a timer