Forecast soundings suggest the potential for MLCAPE on the order of 1,000-1,500 J/kg generally, but perhaps locally 2,000 J/kg where higher dewpoints exist, with cloud tops potentially to 40,000ft (-60C or colder). While flow aloft will be fairly weak (~15kts at 500hPa, for example) a reasonable degree of low-level wind shear is evident with slightly backed near-surface winds. Despite limited shear, the magnitude of instability may be sufficient for the strongest cells to become better organised with potential for some transient supercell characteristics.
This is a ramposauras-rex.
I'm actually flying out of Heathrow at 4pm today, heading SE - could be a little interesting!