SNIP

You are not surely claiming *Graham that it is milder in Cornwall
compared with Swindon in winter because of the N.Atlantic drift?!
It is simply because of Cornwall's proximity to the N.Atlantic and is
surrounded by sea that it is milder!

It's certainly a factor. Just look at maps of winter air & sea
isotherms. The sea is particularly warm off the west coast of the UK
because of the N Atlantic Drift. The strength of the prevailing
westerly determines how far the influence stretches eastwards. In the
case of this January, about as far as the Tamar!

Graham