Back in the late '90s when I got my first diesel (a Citroen AX, with what was at the time the smallest production diesel power plant available) you'd have to wait many seconds for the glow plugs to warm the car before trying to start it. Diesel also freezes in the extreme cold, though that's not really a major issue in the UK. You could also run it on used cooking oil.
In the 20 years since then diesels have undergone massive and very rapid evolutionary changes through tax incentives (massively favoring low CO2, high MPG cars) and resulting fleet buying pressures. The result is what we have now: fabulously complicated, precision-engineered common rail engines with multiple turbochargers, incredible efficiency, almost petrol-like smoothness, weird stuff like urea tanks, and instant starting. If you put old vegetable oil in them they would break instantly and expensively.
I went from that AX in 1995 to a new Jaguar XJ6 in 2008 (via lots of petrol cars). The only thing they had in common was the black pump. In no other way were those engines comparable; the Jag was a beautiful, torquey, silky, rumbling thing that felt like a big V8, did 1,000 miles on a single tank, and beat 911s off the traffic lights (well, until 30mph). The AX was an agricultural dinosaur that deafened anyone in it and was so nose heavy you'd break a sweat parking it. One of those cars I could and did keep in tune with a hammer and a can of WD-40; the other needed a team of factory mechanics with computers and an expensive annual service. I sold it as soon as the warranty expired, but the AX was running fine until my sister drove it into a parked car shortly before I got the XJ.