You're conflating multicultural with multi-ethnic.Still in France house hunting. Incredible value here, looking for a 2 or 3 bed on an acre. Can get a wreck for £50,000, something up together starts at £100,000.
See why Himmy likes it so much. Though he spouts peace and love to ethnics, away from big cities it's about as diverse as a KKK get together. Bottle of decent wine from supermarket from £2 and Jura cheese flavour Brets crisps are addictive. I'm poss a bit too far south for your Bloomers, but just think, we could almost be neighbours. Drop round for a drop of rouge and a natter.
France is equally multi-ethnic, even more so, than UK. But it doesn't have the multicultural richness that UK has.
That might be for several reasons:
1 The multi-ethnic immigrants to France tend come from French former colonies and French overseas territories which already have a rich French culture, e.g language etc, so assimilation into a French culture is facilitated, even seamlessly. Whereas the origin of immigrants to UK, though from similar territories, i.e. former colonies and BOTs, they don't have a British culture embedded into their local culture, so assimilation into any UK culture is a high bar.
Maybe the UK former colonial terriritories and BOTS are more diverse than French former colonies and overseas territories.
2. There is a real French culture throughout France. The same cannot be said about the UK. In UK the regional cultural variations are more pronouced than the regional cultural variations in France. Sure there are regional varaitions in France, but these are limited to superficial issues like: food, music, dance, etc, not to legal, governmental, (petty bureaucracy,) language schooling, etc structures and processes.
3. The French 'culture' is embedded into the French psyche. The same is not true in UK, because there is no 'British culture' to speak of. Maybe due to the centuries old history of UK.
4. Immigrants to France are expected and encouraged to integrate.
5. France is secular, so religious symbols are frequently not allowed.
6. French humour is different.
I suspect there other influences and issues.
But at the end of the day, there are more things that unite us than divide us.