I did wonder; seeing a -10 850 patch reach the UK from the NW is very uncommon; for it to arc around the top of the high and reach S England (the first wave of this in the 12z op) is not something I've seen before.
There's actually a second pulse a few days later which makes it to Kent. I guess that explains the zonal look to the GEFS at the moment - lots of sine waves in evidence, but oscillating around -3C or so down here rather than the usual +2 or so. A few of them briefly touch -10C at the bottom of the sine wave, suggesting the operational isn't alone in propelling remarkably cold air SE'wards.
FWIW, the first pulse of -10s from the NW results in highs of 3C under clear blue skies according to the GFS - interesting to experience, I guess, but those same -10s from the east instead would have resulted in so much more.