The warm plumes continue to drift over the Sahara, and then warm up Moscow. The chilly stuff then hits Britain.
The North Atlantic sea temperatures continue to plunge. If there is a bottom to this, I would expect to be seeing it by now, in the ocean currents. Unfortunately they are working up to be cold in the N. Hemisphere.
Increased permafrost is the first phase of glaciation. It won't actually happen in Britain because it is surrounded by the sea which keeps temperatures up to a cosy -18oC. :) You need a frozen sea, and lots of -40 temps to keep up permafrost.
If this were to be a real ice age, you would need all the land back up to it's regular heights and snow lasting all year. On that day, you would see some real positive feedback. But the permafrost has to come first.
We really need a timelapse of this chart.
It would scare people.
ps. that's the ocean temperatures.