Studying the August storms a bit more this is a more useful summary from the MO and has the radar images I had been looking for https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/weather/learn-about/uk-past-events/interesting/2020/2020_07_august_rain.pdf
also interesting the intense cells are on the left at first then as the trough moves back east they are on the right, presumably to do with the curve of the trough.
this from Nick F’s blog on thunderstorm types looks most accurate
Mesoscale Convective System (MCS) - is a collection of thunderstorms that act as a system. An MCS can spread across several counties and last more than 12 hours. These storm systems can contain supercells and sometimes can develop their own low pressure circulation or Mesoscale convective vortex (MCV). These thunderstorms systems usually form and are driven by strong wind speed shear aloft, if vertical shear (veering winds with height) is strong too, embedded supercells are possible. Severe weather can be produced by these systems, particularly large hail, damaging winds and flooding, tornadoes are also possible with any embedded supercells.
Mesoscale Convective Systems in the UK are relatively rare, occurring once or twice a year on average.