What other countries are you comparing?
Initially over the decades England was the target however immigrants have discovered Scotland - N.Ireland - Wales exist and many are giving England the slip as life is not so pleasant, I have also noted that England is not so popular with Europe and those mistakenly taken for English are very quick to correct the mistake.
From the latter part of your question I figure you are a foreigner to British shores.
The United Kingdom is composed of Scotland,Wales,England and Northern Ireland.l Its only really England you could call multiculturalism
Ireland? Assuming you mean Norn Irn,a United Kingdom is the sum of it's parts surely, multicultural or not?