Que?? Thats a bit harsh!
Sub zero temps were never going to come roaring in overnight, it's more of a slow burner but it's already cold not cool....this is England not Norway!
Just looked at the radar and to me it looks like there's plenty of convection starting to brew and heading towards the coast so regardless of....
Low lapse rate, relatively high pressure without a noticeable upper trough/cold pool and therefore high thickness, and generally not enough moisture or energy to produce any meaningful convection- add this to low wind speeds making any very weak or unlikely for land....quoted above, there are positive signs. It's not going to get any warmer, it's not going to get cool, the temp is on a downward trend my friend so be positive!!