Interesting model runs at the moment, all latching onto a plume scenario next week of various intensity. I wouldn't get too hung up on the exact details at this range, and as ever I would stay very cautious about the suggestion of extreme uppers.. a factor that will come into play is the amount of cloud that is likely to become trapped within what looks a very unstable airmass.
On a personal level these are not my favourite synoptics, give me high pressure overhead/domination rather than a muggy unstable airmass from the south..
Longer term - mid atlantic high/scandi trough scenario a strong likelihood - as low heights to the SW are forced to splinter with associated trough, and high pressure can then build strongly to its north. Orientation of the high is all wrong for an injection of continental warmth, look at the cold uppers on the eastern flank of the high and cold air advection - only one way the core of heights is going and that is west.. We remain locked in a meridional jetstream, and the UK sits on the boundary between the cold and warm side of the jet. Plume events often bring sudden switcharound from heat to chill..