Ruby - I think your interesting stat is also encouraging.
I agree in part about ethnic minorites identifying closely with Britishness - perhaps I should have stated 'recent immigrants from rural Pakistan ...' in my previous post. Older immigrants certainly identify with Britishness, as can be seen in the Indian/Pakistani community's stressing of education + good career, and also in the straight-laced, old-fashioned attitude of older generations of immigrants from Africa and the Caribbean.
My gripe lies with recent immigration policy. John Major's Tory government were quite soft and hopeless concerning immigration, from what I remember. Then New Labour really took dumb immigration policy to new levels of idiocy plus added multiculturalism into the mix - a disastrous combination.
As a result we have FGM, polygamy and heightened terrorist threats that sensible immigration and policy on culture would probably not have allowed.
You seemed you've answered your own question re what is Britishness/British culture - it's made up of Northern Irish, English, Scottish and Welsh culture.