I lived in England where there were a lot of immigrants when I was little.
I grew up in England where there were people from all around the world with different cultures and religions.
この場合、次のような言い方ができますよ。
ーI lived in England where there were a lot of immigrants when I was little.
「幼少期たくさんの移民がいるイギリスに住んでいた」
England where there were a lot of immigrants で「移民の多いイギリス」と言えます。
ーI grew up in England where there were people from all around the world with different cultures and religions.
「世界のいろいろな文化や宗教を持つ人が住むイギリスで育った」
people with different cultures and religions で「いろいろな文化や宗教を持つ人々」
ご参考まで！
I spent most of my youth in England, a country with many immigrants.
"私は移民が多い国、イギリスで幼少期を過ごしました"
- I spent some my youth in England, a country with many immigrants.
- Some of my childhood was spent in England, a country of many immigrants.
私は移民が多い国、イギリスで、幼少期、約１年過ごし、世界にはいろいろな文化、宗教を持つ人がいることを肌で感じた
- I spent roughly a year when I was young in England, a country with many immigrants. There I realized that there are people with various cultures and religion in the world.
カナダ 
アメリカ合衆国 
