Jon O'Rourke wrote:

I remember one occasion talking to Norwich ATC who had observed lightning to
their SE. IIRC the nearest sferics were near Amsterdam.

As a youngster living in Great Yarmouth on the Norfolk coast, I would
often see thunderstorms way out to the east. Many, many years later as
a commercial pilot, I would frequently have to dodge around storms some
40 kms off the Dutch coast. This seemed to be a favoured area for
storm development, especially at night. With more understanding, I
would now presume that one of the contributory factors is a land breeze
convergence.

There is an interesting convergence at this very moment (0940) with a
narrow line of showers running from Weymouth to Norwich. The
converging winds show well on: http://www.xcweather.co.uk/

Jack