Thing is, it's been declining since the 1990s (I've lived in Norfolk since 1986). August has traditionally been a reasonably active month historically, occasionally from late July. Plume events usually delivered something, over the last decade or so they have tended to drift eastwards, either into Benelux or grazing the far SE before entering the N Sea. At the moment the average number of thunder days (if I was being a bit NIMBY-ish) is at best 2 or 3, and that includes storms 30 to 40 miles away. Storm intensity has also diminished accordingly, with no more than half a dozen flashes of lightning seen in a whole year (again, rarely within in 10 miles).
My late father's (as yet unpublished) book on the geographical history of East Anglia, notes "Distinctive features are very helpful in distinguishing one local weather pattern from the others. The fogs and mists at the coasts, the thunderstorms of the boulder clay plateau, the dust storms of Breckland and most striking of all, the flatness of the Fens, encouraging frosts in nearly every month of the year and the famous "Fen blow", now thankfully seldom experienced." (His specialist period was 1700-1850, and draws on such writers as Mary Hardy, who kept a comprehensive weather diary, as well as the Board of Agriculture's reports, among others.