I've taught in both the UK (3 years) and the USA (2 years so far), and it really depends on the school and the culture of the surrounding community. As a new teacher, I found that I was forced to teach every year group and as a result I had to prepare lessons for 7 distinctly different classes and age groups every week. I also had to stand outside during breaks and lunch, and also cover for sick teachers during my free hours.
Other teachers viewed this as the way things were, and wouldn't negotiate with me for less of a variety of classes. I work best when I can focus on one topic and make it fun. I couldn't keep up in the UK, and I was seen by many parents and other teachers as not doing enough even though I was putting in 60-70 hour weeks. I ended up quitting and returning to the USA.
Back in America, I am teaching math, and English. Even with teaching two subjects, I'm only preparing lessons for 4 distinctly different groups of students (my math classes are all 7th grade). This is a lot less work for me, and I can put a lot more effort into teaching interesting and fun lessons. I actually feel like I'm teaching instead of babysitting for the first time in my career.
It sounds like you have a good situation in the UK. I wouldn't suggest switching schools too easily. While I do prefer some aspects of the English education system, my overall experience favored the American system over the English one. YMMV