I’m not sure you understand this concept. There should be the local culture to an area. Different areas of Britain have their own native cultures. If one moves to an area you should get to understand the local traditions, norms and values. Now, of course, many of these spread throughout the nations that make up the UK.
When you move to an area, you should integrate into the local culture.
So for example, someone from London moving to a country village should support the local shop/pub. Not moan about farmers getting up at the crack of dawn and starting farming or that the church bells ring on a Sunday. As an English person they will already have an understanding of the wider customs, history, social norms and values common across England (and those across the other home nations).
If you move here from abroad it’s then one step removed. Someone from say Germany moving to that village will have and understanding of the values across the West but not necessarily local ones to England or that village
If someone moved to that village from America they would be a further step removed than the German needing to assimilate into a more European culture (taken here as being those customs, history, norms and values shared in Europe) then following the path set out for the German)
Someone moving from say Afghanistan will again be yet a further step removed removed and if they moved to that village would need to assimilate into western culture then European wide culture, British wide culture, English culture then the culture of that village.
Of course it’s more complicated than that but hopefully this sets out the issues sufficiently
Each time the culture of origin of the migrant is further removed from the local culture the more difficult it is to integrate and align your own morals, beliefs and actions with the local culture
So hope that has helped with what I meant.
So why is it important that we all share customs, morals beliefs (culture)? Well these things are the glue that holds societies together. People have similar expectations and understandings. This means that there is less conflict and division. Humans are, by instinct tribal creatures, we need ways of defining who is in our tribe (or not a threat) and those outside our tribe )potential threat) The rituals of common customs and experiences bind the tribe together.
Where cultures exist side by side the people exist side by side. Existing side by side is not a society.