It’s no surprise that there was such widespread flooding across the northwest in England and Wales yesterday with these kind of accumulations (fig 3).
You can trace back the low that ended up being the root cause of the flash flooding in Greece in recent days as originating from the remains of what was tropical storm Rina that crossed the UK on Saturday. The Meteorological Institute of Berlin quickly renamed it Numa, but I did think that it would cause problems as it deepened over southern Germany on Sunday. I can’t add much to the fancy graphics and smart suit of Stav Danaos (fig 1), so this animation of 06 UTC MSLP charts for this week over that part of the world will suffice (fig 2). Hopefully the plotted values are the 24 hour rainfall totals might give you an idea of how wet it’s been over parts of Greece.