What you are describing from England is exactly how block scheduling was done in Germany for grades 7 and up. There was always a short break after 45 minutes, to get up and move around, and eat/drink, including halfway through the "double". It was not problematic in any way.
Here in America, you've earned yourself a "Cool story, bro."
Here in America they wouldn't give a break at 45 mins, they would just plow through. My college professors managed to give us a break in the middle of double blocks, but my MS kid doesn't get a break.