You should really go.
If you watched the some of the wedding today, you will know that London is still London to some degree.
And, as Cleese says if you go to places like Bath is more like “the England he grew up in”. I was on the Yorkeshire coast last summer. It was excellent. The largest problem was not muslims. The only ones I ever saw was 40 or so men in saudi beach robes perving on women on the beach.
The largest problem was native British yob culture. People lying in the gutters puking a friday night when you are on the way to a theatre show.
Your Yorkshire trip obviously missed the city of Bradford. A lot of the older mill towns are certainly not "English' by the Cleese method.
The British native welfare class. Eliminating welfare would be the only solution, although an improvement over the current situation would be to scale back welfare benefits to the point where ANY job would be preferable to welfare, along with vigorous penalties for working "off the books" while collecting benefits.