This was posted on Uk-Selfbuild forum today which may be of interest to those contemplating laying concrete between now and next April !
The following are a few points relating to the general guidelines. Most of it is taken from Winter Concreting by Alan Pink (C&CA).
Do not permit mixing or laying of concrete when the air temperature is below 2degC or when it is expected to fall below 2degC within the next few hours. Local conditions may increase the risk of low temperatures (seek local knowledge of frost hollows). Check that aggregates are not frost-bound. Providing the air temperature is above 2degC and if concreting cannot be delayed, frost bound aggregates must be thoroughly heated. Do not permit an unprotected concrete slab to be laid in more than the lightest rain or snow showers. Protect fresh concrete if rain or snow is likely. Hydration reactions will reduce significantly (or cease) below 5degC or so and as such extra time needs to be given to ensure adequate strength gain for serviceability requirements.
In general, the precautions that you mentioned may well be sufficient to protect the concrete initially (they will certainly help) but it's always best to be on the safe side and wait for a warm spell in the weather forecasts.
Rick