Well I am glad you like the books and your question has me wondering. When writing a piece for the RHS in 2006 I compared sowing dates with those of a grower in Scotland and was surprised to find little difference. On the other hand, some sites have a lot more wind and snow than here. I think each gardener has to bear their own climate in mind and alter the dates a little if conditions are adverse at any particular time.
On the other hand I urge you to have a go at, for example, winter salads in a polytunnel because my tunnel freezes hard every winter, inside, and plants mostly survive. They maybe don’t enjoy it and look wiped out when their frozen leaves are flat on the soil (most days last December) but my only losses last winter of tunnel salads were lettuce that succumbed to fungal rot in a damp part of the tunnel, compared to near 100% survival where ventilation (with mostly freezing air) was better.
Protected salads are the main thing to sow now so there is no time to lose and good luck!