I admire your optimism but the England of today is a far cry from the eras you reference. Socialism has taken a heavy toll on the economy and, more significantly, the attitudes of the population. The average age in the UK is 37, meaning that many were born in the last 30 years and have no real grasp of the glories of past British victories over adverse situations - or the same kind of toughness you assume still exists.
I don't wish the Brits any harm (my ancestors were English) and hope your optimism is proven true but I fear that too many British citizens have allowed themselves to become dependent on the government dole and assumed government protection. That being the case, they will fall prey to the millions of Muslims now living, mostly un-assimilated, in merry old England. Many of those Muslims will be only too willing to test the resolve of the English people and their liberal government.
Not every Muslim is a terrorist but, to date, every terrorist has been Muslim.
The rot you speak of is in every Western nation. I don’t doubt you agree. However, not unlike an beaten and abused spouse, at some point, there will be payback.