According to this: https://en.wikipedia.org/wiki/Winter_diesel_fuel#United_Kingdom

We switched over to winter diesel on 16th November. 

 

Normal summer fuel has cloud point of 3c. Below this temperature there could be waxing and cause fuel line and injectors to be blocked. 

Diesel fuel is prone to waxing or gelling in cold weather; both are terms for the solidification of diesel oil into a partially crystalline state. Below the Cloud Point the fuel begins to develop solid wax particles giving it a cloudy appearance. The presence of solidified waxes thickens the oil and clogs fuel filters and injectors in engines. The crystals build up in the fuel line (especially in fuel filters) until the engine is starved of fuel, causing it to stop running.

 

I fuelled up on 15th and parked the car up, not used. The car probably won't be used again until mid-December where we drive long distances to see family. During parked up, the temperature will sure drop below cloud point during night time. 

 

Should I get additives to lower the cloud point of diesel in my tank? 

Or it's nothing to worry, it won't damange my engine at 0-5c temperature range when I need the car? 

Nothing to worry about. The glow plugs will get the initial cylinder temperature up, so I wouldn't be an issue.

 

The other night after coming off a shift, the ambient temperature few a good few hours was below freezing. My car with summer diesel still in didn't flinch in starting up.

 

It's more in the colder countries were the diesel grade and preheaters come into their own.

Don't worry, highly likely that winter diesel had been delivered to your filling station prior to this date, as it is not made after mid October

 

If you are really freaked out, you can always ask the filling station what season spec their most recent delivery was.  Will be on their tanker logs

 

Not to worry as said.   As to the pre heaters / glow plugs and not to worry, that is nonsense, waxed diesel in the tank is waxed diesel.  Hense the winter spec to stop it waxing when cold enough as it has been ready in some parts of the UK.  Colder than at weather stations.