Think my van’s just died. Been pretty cold so had problems starting this morning. Goes now but there’s a lot of white smoke (a bit of black on high rev) the white comes and goes. Been suggested that it might be water in the diesel or even semi frozen diesel. Anyone else experienced this? It was -13 this morning and hasn’t been started for three days.

Pour methanol into diesel, let it mix (give time), start and go. I used to start our Golf Mk1 diesel that way when it was below -30 deg. Celsius.

Could well be semi frozen diesel. The additives used in the uk are nit the same as used in cold countries si maybe some engines struggling with the uks extreme cold at mo

Oil seal in the turbo charger could be leaking when cold?

White smoke from a diesel engine could be normal when it is very humid and cold, the engine is cold, the glow plugs are not working to their full potential as long as the white smoke is not excessive. It also could be an indication of a head gasket sealing problem. Most will not leak after running a while, due to extreme cylinder pressure. After the engine rests with combustion pressure in the coolant system, the coolant can work it’s way back into the cylinders through the failing gasket sealing surface. If this happens and causes a hydro lock condition. Combine that with a high torque diesel starter and you may need a rebuild or possibly a new engine assembly. So make sure that your coolant level is full, and is not dark in color or smells like diesel exhaust (smells like a weird spice in the coolant, almost like someone put black pepper and gunpowder in it)

Check your coolant level,if thats ok it could be a failed egr valve,or failed seal in the turbo housing.

When I start my car it produces some white-ish smoke. Once warm it’s gone. The black smoke comes when I floor the accelerator. Typical for old diesels. Unless you wave winter diesel (continental Europe knows such) the water in it begins to freeze.
You can buy additives, you can buy methanol (denaturated alcohol) from ebay or a DIY store, pour a bit and it’ll probably sort it out.