WAV - you talk about the linking of English folk to English nationalism

First you attempt to construct a fantasy of national identity, then you attempt to link it with rigidly constrained definitions of existing cultural expression, harking back to a "purer" past. This serves both to bolster the legitimacy of the fantasy and to define parameters which mean that a large number of people belong, and a smaller group do not. Moving on you then use the newly defined cultural aspects to make the smaller group seem more different and increasingly less sympathetic, identifying them as the cause of the "weakening" of national identity and the reason why these days the nation is less "English" than in the past.

These are exactly the methods the Nazis employed. They had their definition of good German music and identified "foreign" artistic elements as corrupting and non-German. Step-by-step these seemingly small efforts helped to lead to the unthinkable becoming thinkable.

Isolation, whether cultural or physical, breeds mistrust and stagnation, and eventually leads to inbreeding which would mean an end to the nation you say you want to preserve. The world you describe is limited, dull, uninspired and hateful - a world in your image perhaps? Certainly it seems to have little in common with the richly diverse & vibrant culture of England which was founded on migration, interaction and cultural exchange.