[JayG]

My view is that some seed companies like to suggest a wider range of sowing times than is really sensible because it effectively increases the length of time that people will think it's OK to buy the seeds, (maybe cynical!) and also because there is usually a considerable difference in the onset of spring between the north and south of the UK and of course no two years are the same (true!)

As I previously posted; play safe with sowing times, especially if you lack indoor growing facilities and have no "Plan B".

[Aunt Sally]

I go by the soil conditions. 

It's sopping wet and cold just now so a waste of time sowing outdoors. 

[Thrift]

I go by the soil conditions. 

It's sopping wet and cold just now so a waste of time sowing outdoors. 

Exactly Aunt Sally.

Also if you sow too early in a tunnel or greenhouse it's still very cold and often dripping with condensation so the seedlings are cold and wet. The compost seems to get nasty and sour and the whole experience is miserable. Anyway, it's too cold for me to be standing around doing fiddly jobs.