00z GFS I had a look at, I see the very Cold weather in NE USA, E SE Canada, far NW Atlantic Sea helping create Low Pressure waves on the strong Northwest and North Atlantic Jetstream, UK and West Europe getting some Cold NW or NNW flow, after turning less cold with frosts lifting by Monday and Tuesday.
The UK West and NW Europe looked quite a lot blocked by a Colder Azores High, and some milder weather on 00z GFS just like UKMO 00z, that was tweaked this morning on Netweather- it was quite a cold NW flow for 26th January and through to Thursday 27th, comparing to 192 hrs 27th Thursday on 00z ECMWF they were the same.
It could turn a bit less cold from 28th January to about 31st January, but from 1st to 3rd February I have just check to see the 00z GFS which I favour and trust more than the 06z GFS, it is cold high Azores High, and it has some cold frosty and snowy weather too, with some Beast from the East Low Pressure.
The GFS Ensembles that you have posted, show that return to cold on the 25th for London, but then after that it gets ENS there's lot of scattering on it, ranging from -3 to +2 that sort of.
But I shall see what they show over the next few days.
Climate is warming up, Scotland and N Ireland and North England still often gets some Winter frost, ice and snow, November to March, but the SE and South UK including S Central England and Wales, together with the West and North through the year, they sometimes get more rain than London and S SE England, where some longer dry fine spells without much heavy rain is seen every year.
The North Atlantic Sea often gets some much Colder Wintry conditions from November to March Months, and Mild SW and South winds tend to be more frequent over the East and SE of North Atlantic Sea, as the Azores High tends to stay in charge.
With this warmth and heat, the Central and South UK has become mostly free of snow and frost.