Why do you think England was isolated from the rest of Europe in the first half of the nineteenth century? Isolated in what sense?

I'm not sure it's accurate to say that England was isolated from the rest of Europe. They were certainly involved in continental European affairs politically (e.g. the Congress of Vienna, the Crimean War, the Greek War of Independence), and the same could be said with Britain's economic involvement (e.g. textile markets, foreign capital investment, intensifying level of exports). Moreover, Britain faced the same social problems (a lot of it the result of industrialization) as the rest of Europe.

The only sense it could be said England was "isolated" was geographically, i.e. the diplomatic conception of "splendid isolation" popularized in the late 19th century. In reality, though, that was a false perception, not least for the reasons mentioned above.