There are pros and cons wherever you live. Bleedingly obvious comment but it depends what you like doing and what you're looking for in your life.
I've lived in a smallish Scottish town, a Scottish city, a large city in the N of England, London and rural France. They all had good and bad points.
So my own personal experience and views:
There is some stuff in London that nowhere else will match: the range of theatres, museums, art exhibitions, restaurants and shops. Yes, these things exist elsewhere but not the same variety. Also, the multicultural aspect. I used to love sitting in a cafe and hearing all the different languages around me. I had friends of all ages and nationalities which hasn't been the case in other places I've lived. You feel very anonymous walking around. Nobody cares what you wear or what you look like. Sometimes that felt lonely and sometimes liberating. The parks are great but you are miles from the countryside and the coast. I missed that.
In a small Scottish town people are generally friendly and will take the time to stop and chat, in shop or at a bus stop. The pace is more relaxed. People know each other; that can be nice but also as a young person you can feel rather constrained. Individuality can be viewed judgementally. If you choose the right town you will be near some beautiful countryside. You will not have a big choice of schools. On the other hand almost everyone goes to the local school which in my experience was a good thing.
Life in a large city elsewhere in the UK offers many of the same opportunities as London but with less variety as far as theatre, museums etc go. But you will find plenty of gyms, yoga classes, sports teams, book clubs, language classes etc etc, and good schools if you do your research. If you are on the outskirts of a large city with good transport links, you will be able to get into the countryside easily and into town quickly and for me that's probably the best of both worlds.
Rural France is obviously completely different - fantastic in some ways and less so in others, but I don't think that's relevant to this conversation 