This is why I am baffled as to your definition of multiculturalism. Either we can adopt what you regard as multicultural policies and end up with a monoculture, or we can not adopt multicultural policies and be a monoculture. Does it even matter what policy we choose, then?
Not all paths lead down to cultural decay; people in one country speaking one tongue can hold all the cultures they like - and indeed as you said so yourself, it's possible to hold more than one culture and elements from many cultures. Preserving one doesn't necessitate the destruction of others, but doing nothing does result in one's fall. This is a great problem when it's a culture native to a country, for if it dies there there will be nowhere to reintroduce it from and it'll be just plain up extinct.
Just to be clear, by English you mean "white and English", right? I can't see any other way this statistic works.
There is no 'white' by American definition where 'white' is a diaspora of various white ethnicities, English is what I mean.
I think people with different skin colours are capable of being English. I'll go further - children and particularly grandchildren of immigrants do retain aspects of the culture they arrived with, but are also able to integrate into English society fine - indeed, your own argument on cultural assimilation implies that this is what will happen, unless you're suggesting immigrants have some kind of shield against it.
I'm using the definition where anyone can be British as a sovereign national but English means English, and can't be changed, it's in genetics. English culture can certainly be taken up by anyone though, ethnicity does not dictate culture.
Is it? I can see that integration is helpful in a multicultural society, but I don't see what kind of threat uncontrolled immigration is supposed to represent unless we're in one of those really unrealistic scenarios I mentioned earlier.
Uncontrolled immigration leads to segregation, conflict and poses a burden financially and socially to the host country. This is no unrealistic scenario, this is evident. The threat is that, if we take the melting pot analogy to be the culture, instead of having the soup base 'the native culture' whereupon the spices are built, we instead have various ingredients replacing one another until there is only one grey ingredient in the pot.
No. Your implication with those examples is that if we allow immigration to be unchecked then British culture will end up wiped out, just like the Hakka Chinese. In that regard, we should be seeing minority cultures as threats, not valuable things to be protected. Is that what you were getting at with those examples?
No, also I would not lump all cultures in the British isles as being one culture, each have their own distinct ones. Culture is usually something valuable to be protected; each represents a different way of thinking and viewing the world, something I suppose is undervalued today. Minority cultures are not inherently threats unless they are incompatible with the native culture, the pressing issue is when nothing is done to preserve the native culture that problems arise - Like with the Hakka Chinese.
Even without immigration, a culture can still die simply because no one bothers to preserve it. With unchecked immigration, this process can be instigated or sped up. Large populations of migrants who don't speak the native tongue suddenly showing up and displacing the local population who hold the native culture will result in the destruction of that culture in that area. Steps should be made so that any new cultures arising can coexist with the native culture without necessitating the destruction of one, as in the Hakka Chinese example it would be absurd to say that the only way you could allow it to prosper again would be to destroy the Han Chinese culture [which is in fact, a larger demographic than the Hakka Chinese - they are the minority culture in this regard, I believe you mistakenly think they are the majority]. Something simpler like teaching Hakka Chinese would be enough to preserve the one culture, and in such a way also allow a multiculture to exist. I particularly love the Wales example because of the way they rather easily reversed the decline of Welsh culture by enacting the Welsh Language Act 1993 [which of course was to do with preserving the Welsh language]. You should see declining cultures as threats in of themselves.