GFS lost the plot last night and went from temperatures in the mid teens for northern England next Wednesday, to widespread snow across parts of Wales, Scotland and northern England by the Saturday.
As it stands this morning, it shows temperatures plummeting from the north over Wednesday/Thursday and the risk of snow over Eryri (Snowdonia) and Scottish hills by next weekend. Hill walkers beware! But not the breaking laws of physics winter wonderland that it showed last night.
However this is just one model, though it does sit in the middle of the Ensembles, with a mix of average and more extreme scenarios as solutions.
ECMWF also shows a big cool down from Wednesday/Thursday. It extends to next Saturday at present.
I think if the cool down does occur as rapidly as the models suggest might happen, then the transition could be interesting with squall lines developing across the cold front.
Do remember though that next weekend is way, way off in modelling land and far too early to forecast the weather for then. These are simply computer modelled possible scenarios.